40type of skin disease most important disease treatment investigation finding differential diagnosis contraindication ICU management OPD prescription and detail

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Good. I have confirmed the dermatology textbooks available. Given the breadth of this request (40 diseases × 8 domains each), I'll now compile a comprehensive, authoritative reference using knowledge from Andrews' Diseases of the Skin, Fitzpatrick's Dermatology, and Harrison's Principles — the standard references available in the library.

40 Most Important Skin Diseases — Comprehensive Clinical Reference

HOW TO USE THIS GUIDE

Each disease is presented with:

Clinical Findings | Investigations | Differential Diagnosis | Treatment (OPD Prescription) | Contraindications | ICU Management (where applicable)

1. ATOPIC DERMATITIS (ECZEMA)

Findings: Pruritus, lichenification, flexural involvement (antecubital, popliteal fossae), xerosis, Dennie-Morgan lines, keratoconus. IgE elevated.

Investigations: Serum IgE (elevated), eosinophil count, skin prick tests, patch test (for contact component), SCORAD scoring.

DDx: Contact dermatitis, seborrhoeic dermatitis, scabies, psoriasis, tinea corporis, mycosis fungoides.

OPD Rx:

Emollients (white soft paraffin or aqueous cream) liberally, multiple times daily
Mild-moderate: Hydrocortisone 1% cream BD × 2 weeks
Moderate-severe: Betamethasone valerate 0.1% cream BD (face: use mometasone 0.1%)
Tacrolimus 0.1% ointment (steroid-sparing, especially face/flexures)
Sedating antihistamine: Chlorpheniramine 4 mg TDS (for sleep)
Second-line: Dupilumab 600 mg SC loading then 300 mg SC every 2 weeks (moderate-severe)

Contraindications: Topical steroids on face (fluorinated), systemic steroids in infants, tacrolimus in active skin infections.

ICU Management: Rarely needed; Erythrodermic AD — IV fluids, temperature regulation, topical steroids under occlusion, IV cyclosporine 3–5 mg/kg/day if severe, prophylactic antibiotics for secondary infection (Staphylococcus aureus colonisation).

2. CONTACT DERMATITIS (ALLERGIC & IRRITANT)

Findings: Erythema, vesicles, weeping at site of contact (allergic = delayed, 48–72 hrs); irritant = immediate burning. Positive patch test (allergic type).

Investigations: Patch test (gold standard for allergic type), KOH prep to exclude fungal, skin biopsy if uncertain.

DDx: Atopic dermatitis, seborrhoeic dermatitis, tinea, psoriasis, cellulitis.

OPD Rx:

Remove/avoid allergen or irritant
Clobetasol propionate 0.05% cream BD × 1–2 weeks (severe)
Betamethasone valerate 0.1% cream for moderate
Oral prednisolone 0.5 mg/kg/day tapering over 2 weeks (widespread)
Antihistamines: Cetirizine 10 mg OD
Barrier creams: Zinc oxide ointment

Contraindications: Systemic steroids in diabetic patients (use with caution, monitor glucose), occlusive dressings over infected skin.

ICU: Not typically required unless widespread erythroderma.

3. PSORIASIS

Findings: Well-demarcated silvery scaly plaques on extensor surfaces, scalp, nails (pitting, onycholysis, oil spots). Auspitz sign (pinpoint bleeding on scale removal). Koebner phenomenon.

Investigations: Skin biopsy (Munro microabscesses, parakeratosis), ESR, CRP, HLA-B17/B13/Cw6, joint X-rays if psoriatic arthritis suspected, hepatic function before methotrexate.

DDx: Seborrhoeic dermatitis, tinea corporis, pityriasis rosea, lichen planus, secondary syphilis, mycosis fungoides.

OPD Rx:

Emollients
Mild: Coal tar 2–10% preparations + salicylic acid 2–6%
Moderate: Betamethasone dipropionate 0.05% + calcipotriol (Dovobet) OD
PUVA or Narrowband UVB for extensive disease
Methotrexate 7.5–25 mg/week PO (monitor LFTs, CBC)
Acitretin 25–50 mg/day PO (pustular/erythrodermic)
Biologics: Adalimumab, Secukinumab, Ixekizumab (moderate-severe)

Contraindications: Methotrexate — pregnancy, hepatic disease, active infection, significant alcohol use. Acitretin — pregnancy (teratogenic, avoid conception for 3 years after stopping). Biologics — active TB (screen with TST/IGRA), active hepatitis B, severe cardiac failure.

ICU Management (Erythrodermic/Pustular Psoriasis):

Bed rest, reverse isolation
IV fluids + electrolyte correction
Temperature regulation (blankets, warm IV fluids)
Cyclosporine 3–5 mg/kg/day IV or acitretin 25–50 mg/day
IV antibiotics if secondary infection
Monitor cardiac output, albumin, calcium

4. ACNE VULGARIS

Findings: Comedones (open/closed), papules, pustules, nodules/cysts, post-inflammatory hyperpigmentation, scarring. Predominantly face, back, chest.

Investigations: Hormonal panel (DHEA-S, testosterone, LH:FSH ratio) if PCOS suspected, culture if gram-negative folliculitis suspected.

DDx: Rosacea, folliculitis, perioral dermatitis, milia, sebaceous hyperplasia, keratosis pilaris.

OPD Rx (stepwise):

Mild: Benzoyl peroxide 5% gel OD + adapalene 0.1% gel nocte
Moderate: Add doxycycline 100 mg OD × 3–6 months (or azithromycin 500 mg 3×/week)
Severe nodular: Isotretinoin 0.5–1 mg/kg/day PO × 4–6 months (total dose 120–150 mg/kg)
Women: Co-cyprindiol (Diane-35) if OCP suitable
Topical clindamycin 1% + benzoyl peroxide (BenzaClin)

Contraindications: Isotretinoin — pregnancy (Category X, mandatory contraception + monthly pregnancy tests), hepatic disease, hyperlipidaemia, concurrent tetracyclines. Tetracyclines — pregnancy, children <8 years.

ICU: Not applicable.

5. ROSACEA

Findings: Centrofacial erythema, telangiectasia, papulopustules (but NO comedones — differentiates from acne), rhinophyma, ocular involvement (blepharitis, conjunctivitis). Flushing triggered by alcohol, heat, spicy food.

Investigations: Clinical diagnosis. Demodex mite examination (skin surface biopsy) if refractory. Exclude lupus (ANA).

DDx: Acne vulgaris, SLE (butterfly rash), seborrhoeic dermatitis, perioral dermatitis, carcinoid syndrome.

OPD Rx:

Avoid triggers
Topical: Metronidazole 0.75% gel BD or azelaic acid 15% gel BD
Oral: Doxycycline 40 mg/day modified-release (anti-inflammatory dose, not antibiotic dose) × 3 months
Severe: Oral isotretinoin 0.5 mg/kg/day
Rhinophyma: CO₂ laser, surgery
Ocular: Lid hygiene + doxycycline

Contraindications: Topical steroids (cause steroid-induced rosacea/rebound), doxycycline in pregnancy/children.

6. URTICARIA (HIVES)

Findings: Transient (<24h per lesion) wheals, erythema, intense pruritus. Angioedema if deep dermis involved. Dermographism. Classified: acute (<6 weeks), chronic (>6 weeks).

Investigations: Full blood count, ESR, CRP, ANA, thyroid antibodies, H. pylori serology, stool for parasites, IgE RAST panel, C3/C4 (if angioedema).

DDx: Urticarial vasculitis (lesions >24h, bruise), erythema multiforme, bullous pemphigoid (urticarial phase), mastocytosis.

OPD Rx:

Cetirizine 10 mg OD (or loratadine 10 mg OD) — non-sedating
Increase to 4× standard dose if inadequate
Add ranitidine 150 mg BD (H2 blocker, adjunct)
Refractory chronic: Omalizumab 300 mg SC monthly
Short course prednisolone 0.5 mg/kg/day × 5 days for acute severe

Contraindications: Sedating antihistamines in elderly (fall risk), epinephrine auto-injectors (EpiPen) only for anaphylaxis, not isolated urticaria.

ICU (Anaphylaxis/Angioedema with airway compromise):

Epinephrine 0.5 mg IM (1:1000) — thigh
IV hydrocortisone 200 mg
IV chlorpheniramine 10 mg
Airway management: intubation if laryngeal oedema
IV fluids for hypotension
C1-esterase inhibitor concentrate if hereditary angioedema

7. SCABIES

Findings: Intense nocturnal pruritus, burrows in web spaces/wrists/genitalia/areolae, papules, excoriations. Norwegian (crusted) scabies in immunocompromised.

Investigations: Dermoscopy (delta-wing jet with contrail), skin scraping + KOH microscopy (mite, eggs, faeces), skin biopsy (eosinophilic infiltrate).

DDx: Atopic dermatitis, contact dermatitis, folliculitis, delusions of parasitosis, varicella.

OPD Rx:

Permethrin 5% cream — apply neck to toe, leave 8–12 hours, repeat in 1 week (all household contacts simultaneously)
Alternative: Ivermectin 200 mcg/kg PO × 2 doses (D1 and D14)
Antipruritic: Hydroxyzine 25 mg nocte or calamine lotion
Treat all clothing/bedding (60°C wash or bag for 72h)

Contraindications: Permethrin — infants <2 months (benzyl benzoate or sulphur 6% in those cases). Ivermectin — pregnancy, breastfeeding, children <15 kg.

ICU (Norwegian scabies): Barrier nursing, IV ivermectin protocol if available, keratolytics (salicylic acid 10%) to remove hyperkeratotic scale, treat secondary bacterial infection.

8. TINEA INFECTIONS (DERMATOPHYTOSIS)

Subtypes: Tinea pedis, cruris, corporis, capitis, unguium (onychomycosis), versicolor (Malassezia — not dermatophyte).

Findings: Annular scaling plaques with central clearing, pruritus; nail: thickening, discolouration, subungual debris; scalp: alopecia, kerion.

Investigations: KOH preparation (hyphae), Wood's lamp (M. canis — green fluorescence), fungal culture (Sabouraud's agar), skin biopsy with PAS stain.

DDx: Psoriasis, eczema, pityriasis rosea, erythrasma, granuloma annulare.

OPD Rx:

Superficial (body/groin/foot): Clotrimazole 1% cream BD × 2–4 weeks or terbinafine 1% cream OD × 1 week
Scalp/nail (systemic needed): Terbinafine 250 mg/day × 6 weeks (fingernail), 12 weeks (toenail)
Fluconazole 150 mg weekly × 6–12 months (onychomycosis)
Kerion: Add prednisolone 1 mg/kg/day × 2 weeks to antifungal

Contraindications: Terbinafine — active liver disease (hepatotoxic). Itraconazole — heart failure, drug interactions (CYP3A4 inhibitor).

9. CANDIDIASIS (CUTANEOUS)

Findings: Beefy red plaques with satellite pustules in moist body folds (inframammary, axilla, groin, nappy area), white pseudomembrane in oral thrush, pruritus/burning.

Investigations: KOH prep (pseudohyphae + budding yeasts), culture, blood culture (systemic), blood glucose (screen for diabetes).

DDx: Intertrigo, tinea, contact dermatitis, inverse psoriasis, erythrasma.

OPD Rx:

Topical: Clotrimazole 1% cream BD or nystatin cream BD × 2 weeks
Oral (oropharyngeal): Fluconazole 150 mg PO single dose or nystatin suspension 100,000 units QDS × 7 days
Keep folds dry; antifungal powder (miconazole)

Contraindications: Fluconazole — pregnancy (animal teratogen), avoid with drugs prolonging QT.

ICU (Systemic/Invasive Candidiasis):

Caspofungin 70 mg IV loading then 50 mg/day (first line in critically ill)
Or fluconazole 800 mg IV loading then 400 mg/day (fluconazole-susceptible)
Remove/replace central lines
Ophthalmology review (endophthalmitis)
Echocardiogram to exclude endocarditis

10. HERPES SIMPLEX (HSV 1 & 2)

Findings: Grouped vesicles on erythematous base → painful ulcers, healing with crust. Oral (HSV-1): cold sores. Genital (HSV-2): painful genital ulcers + tender inguinal lymphadenopathy. Primary worse than recurrence. Eczema herpeticum (superimposed on atopic skin).

Investigations: Tzanck smear (multinucleated giant cells), PCR (gold standard), viral culture, direct fluorescent antibody, serology (HSV IgG/IgM).

DDx: Herpes zoster, aphthous ulcers, syphilitic chancre (painless), chancroid (painful, soft), impetigo, Behçet's disease.

OPD Rx:

Primary: Aciclovir 400 mg TDS × 7–10 days (or valaciclovir 1 g BD × 10 days)
Recurrence: Aciclovir 400 mg TDS × 5 days (start at prodrome)
Suppression: Valaciclovir 500 mg OD
Topical: Aciclovir 5% cream 5× daily (mild labial)

Contraindications: Aciclovir — caution in renal impairment (dose reduce). Avoid kissing/sexual contact during active lesions.

ICU (Eczema herpeticum / Herpes encephalitis):

IV aciclovir 5–10 mg/kg 8-hourly × 14–21 days
Monitor renal function, hydrate well
Neurological monitoring if CNS involvement

11. HERPES ZOSTER (SHINGLES)

Findings: Prodromal pain → unilateral dermatomal vesicles → crusting over 3–5 weeks. Postherpetic neuralgia (PHN) most common complication. Ramsay Hunt syndrome (facial palsy, ear vesicles, tinnitus — CN VII/VIII).

Investigations: Clinical diagnosis. PCR of vesicle fluid (confirm), VZV DFA, serology, blood count (lymphocyte count — screen for immunosuppression).

DDx: Herpes simplex, cellulitis, contact dermatitis, impetigo, early zoster (pre-vesicular phase resembles musculoskeletal pain).

OPD Rx:

Aciclovir 800 mg 5× daily × 7 days (within 72h of rash) or valaciclovir 1 g TDS × 7 days
Pain: Paracetamol ± NSAIDs; gabapentin 300–900 mg TDS; amitriptyline 10–75 mg nocte (PHN)
Topical calamine for itch
Vaccination: Shingrix (recombinant zoster vaccine) 2 doses

Contraindications: Aspirin — Reye syndrome risk in children. Live zoster vaccine contraindicated in immunocompromised (use recombinant).

ICU (Disseminated VZV / Visceral involvement):

IV aciclovir 10 mg/kg 8-hourly × 7 days
Isolation (airborne + contact precautions)
Monitor liver, lung (VZV pneumonitis), brain (VZV encephalitis)

12. IMPETIGO

Findings: Non-bullous: honey-coloured crusted lesions around mouth/nose (Staph. aureus / Strep. pyogenes). Bullous: flaccid bullae → shallow erosions (Staph. aureus phage type 71, exfoliative toxin). Ecthyma: deeper crusted ulcers.

Investigations: Wound swab (culture + sensitivity), ASOT if post-streptococcal complications (glomerulonephritis) suspected, urine dipstick.

DDx: Herpes simplex (grouped vesicles), eczema herpeticum, pemphigus, contact dermatitis, chickenpox.

OPD Rx:

Localised: Mupirocin 2% ointment TDS × 5–7 days or fusidic acid cream TDS
Widespread: Flucloxacillin 500 mg QDS × 7 days PO (or cefalexin 500 mg QDS)
MRSA: Co-trimoxazole 960 mg BD or doxycycline
Decontamination: Chlorhexidine washes, nasal mupirocin

Contraindications: Mupirocin overuse — risks resistance development.

ICU (SSSS — Staphylococcal Scalded Skin Syndrome):

IV flucloxacillin 1–2 g 4-hourly
IV fluids, electrolyte management (like burns)
Wound care with non-adherent dressings
Avoid systemic corticosteroids (worsen SSSS)
Temperature regulation, nutritional support

13. CELLULITIS & ERYSIPELAS

Findings: Cellulitis: warm, tender, poorly demarcated erythema, oedema, lower limbs (Staph. / Strep.). Erysipelas: bright red, raised, sharply demarcated (Strep. pyogenes), butterfly on face.

Investigations: Full blood count (WBC, CRP, ESR), blood cultures (bacteraemia), wound swab, ultrasound (exclude deep abscess/necrotising fasciitis), ASO titre.

DDx: DVT, lipodermatosclerosis, contact dermatitis, eosinophilic cellulitis, necrotising fasciitis (needs urgent exclusion).

OPD Rx (mild):

Cefalexin 500 mg QDS × 7 days (or co-amoxiclav 625 mg TDS)
Penicillin V 500 mg QDS (erysipelas — streptococcal)
Elevate limb, mark borders
Prophylaxis if recurrent: Phenoxymethylpenicillin 250 mg BD for ≥6 months

Contraindications: Penicillin allergy — use clindamycin 300 mg QDS.

ICU (Septic cellulitis / Necrotising fasciitis):

IV co-amoxiclav 1.2 g TDS + clindamycin 900 mg TDS (anti-toxin effect)
MRSA suspected: Add vancomycin or linezolid
Necrotising fasciitis: EMERGENCY surgical debridement + piperacillin/tazobactam + clindamycin + IVIG
Monitor: sepsis parameters, lactate, CT/MRI (gas in soft tissues = necrotising fasciitis)

14. CHICKENPOX (VARICELLA)

Findings: Fever → pruritic vesicles in crops ("dewdrop on rose petal"), centripetal distribution (trunk>face>limbs), all stages simultaneously. Complications: pneumonia (adults), encephalitis, secondary bacterial infection.

Investigations: Clinical diagnosis; PCR, DFA, or Tzanck smear if uncertain; CXR if respiratory symptoms; LFTs.

DDx: Disseminated herpes zoster, insect bites, impetigo, hand-foot-mouth disease, smallpox.

OPD Rx:

Supportive: Paracetamol (NOT aspirin), calamine lotion, chlorpheniramine 4 mg TDS (itch)
Aciclovir 800 mg 5× daily × 7 days in adults >13 yrs, immunocompromised, pregnant, severe disease
VZV immunoglobulin post-exposure prophylaxis (within 96h) for high-risk contacts

Contraindications: Aspirin — Reye syndrome. Oral steroids — worsen severity.

ICU (Varicella pneumonia / Encephalitis):

IV aciclovir 10 mg/kg 8-hourly × 7–10 days
Respiratory support (oxygen, mechanical ventilation if needed)
Isolation (airborne precautions)

15. MOLLUSCUM CONTAGIOSUM

Findings: Dome-shaped, flesh-coloured, umbilicated papules 2–5 mm, trunk/face/genitalia, multiple lesions in immunocompromised (HIV). Spread by direct contact/autoinoculation.

Investigations: Clinical diagnosis. Biopsy (Henderson-Paterson/molluscum bodies on histology) if atypical. HIV test if widespread/giant lesions.

DDx: Warts, basal cell carcinoma (pearly), keratoacanthoma, dermatofibromas, Cryptococcus (HIV).

OPD Rx:

Often self-limiting (6–18 months); treatment if cosmetically bothersome
Cryotherapy (liquid nitrogen)
Curettage
Topical imiquimod 5% cream 3× weekly × 16 weeks
Topical potassium hydroxide 10% solution (apply once daily until inflammatory response)
Cidofovir cream in HIV (off-label)

Contraindications: Imiquimod — pregnancy (limited safety data).

16. WARTS (VERRUCA VULGARIS — HPV)

Findings: Common warts (HPV 2,4): rough exophytic papules on hands. Plantar warts (verruca): endophytic, painful, black dots (thrombosed capillaries). Genital warts (HPV 6,11): soft cauliflower-like condylomata acuminata.

Investigations: Clinical diagnosis. Biopsy if atypical. HPV typing (16,18 — high risk for malignancy). Acetic acid test (genital warts whiten).

DDx: Molluscum, seborrhoeic keratosis, callus (no black dots), squamous cell carcinoma (SCC).

OPD Rx:

Salicylic acid 15–26% solution OD (after soaking and filing)
Cryotherapy (liquid nitrogen) every 2–3 weeks
Podophyllotoxin 0.5% solution BD × 3 days/week × 4 weeks (genital warts)
Imiquimod 5% cream (genital warts) 3× weekly
Laser ablation for resistant cases
HPV vaccination (Gardasil 9): prevention

Contraindications: Podophyllin — pregnancy (teratogenic). Cryotherapy — care on digital nerves.

17. PEMPHIGUS VULGARIS

Findings: Flaccid bullae on normal-appearing skin → extensive erosions, mucous membrane involvement (painful oral ulcers often first). Nikolsky sign positive (lateral pressure → blister extension). Asboe-Hansen sign positive. Often fatal if untreated.

Investigations: Skin biopsy: intraepidermal acantholysis (biopsy from edge of blister). DIF: IgG deposits in intercellular spaces ("chicken wire"). Serum anti-desmoglein (Dsg) 1 and 3 antibodies (ELISA — titre correlates with disease activity).

DDx: Bullous pemphigoid (tense bullae, no mucosa, negative Nikolsky), erythema multiforme, staphylococcal scalded skin, linear IgA disease.

OPD Rx:

Prednisolone 1–1.5 mg/kg/day (high dose, prolonged taper)
Adjuvant (steroid-sparing): Azathioprine 1–3 mg/kg/day or mycophenolate mofetil 2 g/day
Rituximab 1000 mg IV × 2 doses (2 weeks apart) — first-line option for moderate-severe
Wound care, antiseptic mouthwash, high-protein diet

Contraindications: NSAIDs — some drugs trigger pemphigus (penicillamine, captopril, rifampicin). Azathioprine requires TPMT testing before starting.

ICU (Widespread erosions/Sepsis):

IV methylprednisolone 500 mg–1 g/day × 3 days (pulse)
IV rituximab if available
Burns protocol wound care (non-adherent dressings)
IV antibiotics for secondary infection (flucloxacillin / vancomycin)
Nutritional support (TPN if oral involvement severe)
Monitor fluid balance, albumin, electrolytes
Caution with corticosteroid complications (hyperglycaemia, GI bleeds, sepsis)

18. BULLOUS PEMPHIGOID

Findings: Tense bullae on erythematous base in elderly, trunk/flexures, pruritic urticarial plaques preceding bullae, mucous membrane spared (in most). Nikolsky sign negative.

Investigations: Skin biopsy (subepidermal bulla, eosinophilic infiltrate). DIF: Linear IgG and C3 at BMZ. Serum anti-BP180 (NC16A domain) and anti-BP230 antibodies.

DDx: Pemphigus vulgaris, dermatitis herpetiformis, linear IgA disease, erythema multiforme, bullous drug eruption.

OPD Rx:

Potent topical corticosteroid (clobetasol propionate 40 g/day — whole body): equal/better than systemic in moderate disease
Doxycycline 200 mg/day + nicotinamide 1.5 g/day (anti-inflammatory, fewer side effects)
Prednisolone 0.5–0.75 mg/kg/day if extensive
Azathioprine or mycophenolate mofetil (steroid-sparing)

Contraindications: Long-term systemic steroids in elderly — osteoporosis, diabetes, cataracts. Always co-prescribe PPI, calcium+vitamin D.

ICU: If widespread blistering/superinfection — similar to pemphigus management above.

19. DERMATITIS HERPETIFORMIS

Findings: Intensely pruritic papulovesicles on extensor surfaces (elbows, knees, buttocks, scalp), symmetric. Associated with coeliac disease/gluten-sensitive enteropathy (90%).

Investigations: DIF of perilesional skin (granular IgA at dermal papillae tips — pathognomonic). Serum IgA anti-tissue transglutaminase, anti-endomysial antibodies, anti-deamidated gliadin. Jejunal biopsy (villous atrophy). Full blood count (iron deficiency anaemia).

DDx: Bullous pemphigoid, linear IgA disease, atopic eczema, scabies.

OPD Rx:

Dapsone 50–200 mg/day PO (rapid response within 24–48h) — controls skin, NOT gut
Strict gluten-free diet (controls both skin and gut, allows dapsone reduction/withdrawal over months-years)
Folic acid supplementation with dapsone

Contraindications: Dapsone — G6PD deficiency (haemolysis), sulphonamide allergy, severe anaemia. Screen G6PD before starting.

20. ERYTHEMA MULTIFORME (EM) / STEVENS-JOHNSON SYNDROME (SJS) / TOXIC EPIDERMAL NECROLYSIS (TEN)

A. Erythema Multiforme (Minor/Major)

Findings: Target lesions (3 zones: central dark/blister, pale middle, outer erythema), acral distribution, triggered by HSV (most common), Mycoplasma.

Rx: Treat trigger. Oral aciclovir for HSV-associated EM. Antihistamines for itch. Topical steroids for lesions.

B. SJS (<10% BSA involvement) / TEN (>30% BSA)

Findings: Painful skin necrosis, sheet-like epidermal detachment, severe mucous membrane erosions (oral, ocular, genital), fever, systemic toxicity. Most caused by drugs (sulphonamides, allopurinol, carbamazepine, phenytoin, NSAIDs, lamotrigine). SCORTEN score predicts mortality.

Investigations: Skin biopsy (full-thickness epidermal necrosis — diagnostic). FBC, U&E, LFTs, CXR, blood cultures. Ophthalmology review (ocular involvement → blindness). HLA-B*5801 (allopurinol-TEN in Asian populations).

DDx: Pemphigus vulgaris, SSSS (children, Nikolsky+ but no mucosa, superficial biopsy), generalised fixed drug eruption, necrotising fasciitis.

ICU Management (SJS/TEN — CRITICAL):

STOP causative drug IMMEDIATELY (mortality directly related to time of drug discontinuation)
Transfer to burns unit or ICU
IV fluids (Parkland formula based on BSA involved)
Non-adherent wound dressings (Mepitel, Biobrane)
Eye care: Symblepharon prevention (lubricants, amniotic membrane)
Oral hygiene: Chlorhexidine mouthwash, analgesia
Nutritional support: NGT feeding (high calorie/protein)
Temperature regulation (warm environment — high insensible losses)
Cyclosporine 3 mg/kg/day IV — evidence supports early use
IVIG 1 g/kg/day × 3 days — alternative/adjunct
Controversial: systemic steroids (not routinely recommended)
Antimicrobials: Only for proven secondary infection (NOT prophylactic)

Contraindications in TEN: Systemic steroids (increase infection risk, no survival benefit in most studies), re-challenge with causative drug (life-threatening), prophylactic antibiotics.

21. DRUG ERUPTIONS (FIXED DRUG ERUPTION — FDE)

Findings: Solitary/multiple well-demarcated dusky/violaceous macules or bullae at SAME site on each re-exposure. Residual hyperpigmentation. Common drugs: NSAIDs, tetracycline, co-trimoxazole, paracetamol.

Investigations: Oral provocation test (confirmed diagnosis), patch test at site, biopsy (interface change, melanin in macrophages).

DDx: Herpes simplex, cellulitis, contact dermatitis, melanoma.

OPD Rx: Stop offending drug. Topical steroid. Antihistamine. No re-challenge.

22. DRUG RASH WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS SYNDROME)

Findings: Morbilliform rash (2–8 weeks after drug initiation), fever, lymphadenopathy, facial oedema, visceral involvement (hepatitis, nephritis, pneumonitis, myocarditis). Eosinophilia, atypical lymphocytes. Common drugs: allopurinol, carbamazepine, lamotrigine, dapsone, vancomycin.

Investigations: FBC (eosinophilia), LFTs, renal function, CK, urine analysis, chest X-ray, skin biopsy. HHV-6 and HHV-7 reactivation (markers of DRESS).

DDx: SJS/TEN, serum sickness, hypereosinophilic syndrome, lymphoma.

ICU/Hospital Management:

STOP causative drug
Prednisolone 0.5–1 mg/kg/day × prolonged taper (3–6 months)
Cyclosporine if refractory
Organ-specific management (hepatology, nephrology, pulmonology involvement)
Monitor for reactivation/relapse during steroid taper

Contraindications: Early steroid withdrawal — DRESS has late relapses.

23. MELANOMA

Findings: Asymmetric, irregular Border, multiple Colours (black, brown, red, white), Diameter >6 mm, Evolution (ABCDE rule). Nodular melanoma: rapidly growing dark nodule. Subungual: Hutchinson's sign (pigment extends onto nailfold).

Investigations: Dermoscopy, excision biopsy (4–6 mm margin initially) with Breslow thickness, Clark's level, ulceration, mitotic rate, sentinel lymph node biopsy (Breslow >1 mm), CT thorax/abdomen/pelvis (staging), PET-CT, BRAF mutation testing (treatment selection), LDH.

DDx: Seborrhoeic keratosis, blue naevus, pigmented BCC, compound naevus, dermatofibroma.

Treatment:

Surgical excision margins based on Breslow: In situ → 5 mm; <1 mm → 1 cm; 1–2 mm → 1–2 cm; >2 mm → 2–3 cm
Stage III/IV: Immunotherapy (pembrolizumab/nivolumab) ± ipilimumab; BRAF-mutant: dabrafenib + trametinib
Adjuvant: Pembrolizumab/nivolumab (Stage IIB–III)
Radiotherapy for brain metastases

Contraindications: Immunotherapy — active autoimmune disease, organ transplant. BRAF inhibitors — NRAS mutation (paradoxical activation).

24. BASAL CELL CARCINOMA (BCC)

Findings: Pearly/translucent papule with rolled edges + telangiectasia, may ulcerate (rodent ulcer). Sun-exposed areas (nose, cheeks). Most common skin malignancy.

Investigations: Dermoscopy, punch or excision biopsy (histology: palisading basal cell nests, retraction artefact), CT/MRI for locally advanced.

DDx: SCC, melanoma (nodular), dermatofibroma, sebaceous hyperplasia, merkel cell carcinoma.

Treatment:

Excision with 3–4 mm margin (primary treatment)
Mohs micrographic surgery (high-risk/recurrent/H-zone)
Radiotherapy (elderly, inoperable)
Imiquimod 5% cream or 5-FU (superficial BCC)
Vismodegib (hedgehog inhibitor): locally advanced/metastatic/Gorlin's syndrome

Contraindications: Vismodegib — pregnancy (embryotoxic), must use reliable contraception.

25. SQUAMOUS CELL CARCINOMA (SCC)

Findings: Keratotic papule/nodule on sun-damaged skin, ulcerated, firm, may arise in actinic keratosis, chronic wounds, scars. Risk of metastasis (3–5%), higher in immunosuppressed.

Investigations: Excision biopsy (depth/grade), sentinel lymph node biopsy (high-risk), CT neck/chest, HPV typing (SCCs of lip, tongue — HPV 16).

DDx: BCC, keratoacanthoma, Bowen's disease, melanoma, merkel cell carcinoma.

Treatment:

Excision 4–6 mm margins (low-risk); wider for high-risk
Mohs surgery (face, ears, lip)
Radiotherapy (post-op or primary)
Cemiplimab (anti-PD1) — locally advanced/metastatic SCC
Actinic keratosis prevention: sunscreen, 5-FU cream, ingenol mebutate, photodynamic therapy

Contraindications: Immunosuppression post-organ transplant dramatically increases SCC risk — minimise azathioprine, switch to mTOR inhibitors.

26. VITILIGO

Findings: Well-demarcated depigmented (chalk-white) macules/patches, Koebner phenomenon, Wood's lamp (accentuated fluorescence). Segmental vs non-segmental. Associated autoimmune diseases (thyroid, diabetes, Addison's).

Investigations: Wood's lamp exam, thyroid function tests, thyroid antibodies, FBC (pernicious anaemia), blood glucose, ANA, ophthalmology review (uveitis risk).

DDx: Pityriasis alba, tinea versicolor (hypopigmented, not depigmented), post-inflammatory hypopigmentation, chemical leucoderma, pityriasis versicolor.

OPD Rx:

Face/skin fold: Tacrolimus 0.1% ointment BD (superior for sensitive areas)
Body: Mometasone 0.1% ointment OD (6 weeks on/2 weeks off)
Narrowband UVB phototherapy (2–3× weekly — best for generalised)
Excimer laser (segmental, focal)
Surgical: Split-thickness skin grafting / melanocyte transfer (stable vitiligo)
Ruxolitinib 1.5% cream BD (JAK inhibitor — FDA approved 2022)
Sunscreen (prevent accentuation)

Contraindications: PUVA therapy — hepatic disease, photosensitive drugs, cataracts; children <12 years.

27. ALOPECIA AREATA

Findings: Round/oval patches of non-scarring hair loss, exclamation-mark hairs at margins, smooth scalp. Ophiasis pattern (occipital), alopecia totalis (entire scalp), alopecia universalis (entire body).

Investigations: Trichoscopy (dermoscopy of scalp), biopsy (peribulbar lymphocytic infiltration — "swarm of bees"), thyroid function, ANA (associated autoimmune conditions).

DDx: Tinea capitis (broken hairs, scaling), trichotillomania (irregular borders), traction alopecia, secondary syphilis, androgenetic alopecia.

OPD Rx:

Patchy limited: Intralesional triamcinolone 5–10 mg/mL injections q4–6 weeks (first-line)
Topical: Mometasone 0.1% solution + minoxidil 5% foam
Extensive/rapid: Prednisolone 40 mg/day × 4 weeks then taper
Baricitinib (JAK1/2 inhibitor) 4 mg OD — FDA approved (2022) for severe alopecia areata
Ritlecitinib (JAK3/TEC inhibitor) — approved 2023

Contraindications: Baricitinib — active infection, malignancy, pregnancy, severe renal impairment, venous thromboembolism history.

28. LICHEN PLANUS

Findings: 6 P's: Pruritic, Planar (flat-topped), Purple, Polygonal Papules, wrist/ankle/genitalia. Wickham's striae (white lines on surface). Köbner phenomenon. Oral: white lacy pattern on buccal mucosa. Nail: pterygium, 20-nail dystrophy.

Investigations: Skin biopsy (band-like T-cell infiltrate at DEJ, sawtooth rete ridges, vacuolar degeneration of basal layer). Hepatitis B and C serology (LP association). DIF (fibrinogen deposits at DEJ).

DDx: Psoriasis, lichenoid drug eruption (drugs: gold, antimalarials, ACE inhibitors), secondary syphilis, pityriasis rosea, lichen nitidus.

OPD Rx:

Topical: Clobetasol propionate 0.05% OD × 4–8 weeks
Oral: Prednisolone 30–40 mg/day × 4–6 weeks (widespread/oral)
Tacrolimus 0.1% ointment (oral LP, genital LP)
Hydroxychloroquine 200 mg BD (resistant cases)
Acitretin 25–30 mg/day (severe)
Treat hepatitis C if associated (LP often resolves)

Contraindications: Stop offending drugs (lichenoid reactions). Acitretin — pregnancy.

29. SEBORRHOEIC DERMATITIS

Findings: Greasy yellow-white scales on erythematous base, seborrhoeic areas (scalp, nasolabial folds, eyebrows, chest). Dandruff (scalp only, less inflamed). Associated with Malassezia furfur overgrowth. Common in HIV/Parkinson's.

Investigations: Clinical diagnosis. KOH (exclude tinea). HIV test if severe/refractory. Skin biopsy (spongiosis, perifollicular scale) if uncertain.

DDx: Psoriasis, rosacea, contact dermatitis, atopic dermatitis, tinea faciei.

OPD Rx:

Scalp: Ketoconazole 2% shampoo 2× weekly (leave 5 min), selenium sulphide 2.5% shampoo, or zinc pyrithione
Face/body: Ketoconazole 2% cream BD × 4 weeks, then maintenance 1× weekly
Mild topical steroid (hydrocortisone 1%) short-term for inflammation
Maintenance: Coal tar shampoo, piroctone olamine

Contraindications: Fluorinated steroids on face, prolonged use of topical steroids.

30. PITYRIASIS ROSEA

Findings: Herald patch (solitary ovoid salmon-pink plaque with collarette scaling, 2–10 cm) → secondary eruption after 1–2 weeks (smaller lesions on trunk, "Christmas tree" pattern along Langer's lines). Associated HHV-6/7.

Investigations: Clinical diagnosis. VDRL/RPR to exclude syphilis (secondary syphilis mimics PR exactly). KOH (exclude tinea).

DDx: Secondary syphilis (ALWAYS exclude — serology mandatory), tinea corporis, drug eruption, guttate psoriasis.

OPD Rx:

Usually self-limiting (6–12 weeks)
Emollients + cetirizine 10 mg OD (itch)
Aciclovir 400 mg 5× daily × 1 week (may shorten course, especially if started early — HHV association)
Narrowband UVB (extensive/persistent)

Contraindications: No specific contraindications. Topical steroids only for severe pruritus (short course).

31. PITYRIASIS VERSICOLOR (TINEA VERSICOLOR)

Findings: Hypo/hyperpigmented coalescing macules with fine bran-like scale (Malassezia globosa/furfur), trunk/upper arms, more prominent after suntan. Wood's lamp: yellowish-green fluorescence.

Investigations: KOH prep (spaghetti and meatball appearance — short hyphae + round spores), Wood's lamp, Swartz-Medrik stain.

DDx: Vitiligo (no scale, sharp borders), seborrhoeic dermatitis, pityriasis alba, tinea corporis.

OPD Rx:

Selenium sulphide 2.5% shampoo (apply to affected skin for 10 min before shower) × 2 weeks
Ketoconazole 2% shampoo (same method)
Ketoconazole 2% cream BD × 2 weeks
Oral: Fluconazole 400 mg single dose or itraconazole 200 mg OD × 5 days (extensive/recurrent)
Maintenance: Selenium sulphide/ketoconazole shampoo monthly

32. ERYTHRODERMA (EXFOLIATIVE DERMATITIS)

Findings: Generalised erythema + scaling involving >90% BSA, generalised lymphadenopathy, oedema, loss of temperature regulation, high-output cardiac failure, hypoalbuminaemia. Causes: psoriasis (25%), eczema (25%), drugs (15%), lymphoma/mycosis fungoides (10–15%), unknown (10–20%).

Investigations: Skin biopsy × 3 (serial biopsies — find cause), CBC (eosinophilia, atypical lymphocytes), serum protein/albumin, T-cell receptor gene rearrangement (lymphoma), flow cytometry, CXR, CT body.

DDx: Based on underlying cause (psoriasis, eczema, cutaneous T-cell lymphoma, drug eruption, Sézary syndrome).

ICU Management:

Admit (all erythroderma warrants admission)
Temperature regulation (blankets, warm room)
IV fluids + colloid (albumin) replacement
Electrolyte monitoring
Treat underlying cause: Methotrexate/cyclosporine (psoriasis), cyclosporine (eczema), CHOP (lymphoma)
Treat secondary infection (topical antiseptics, systemic antibiotics)
Venous thromboembolic prophylaxis (high risk)
Nutritional support
Monitor cardiac output (high-output failure risk)

OPD (if stable after treatment): Emollients + weak topical steroid; address underlying cause.

33. MYCOSIS FUNGOIDES (CUTANEOUS T-CELL LYMPHOMA — CTCL)

Findings: Stages: Patch (scaly, eczematous-like patches, photprotected areas) → Plaque (indurated) → Tumour (nodules, ulcerate). Sézary syndrome = erythroderma + circulating Sézary cells (>1000/μL). Alopecia, leonine facies.

Investigations: Skin biopsy with immunohistochemistry (CD3+, CD4+, CD8-, loss of CD7), T-cell receptor clonality by PCR, peripheral blood flow cytometry, CT chest/abdomen/pelvis, PET-CT, blood count + Sézary cell count.

DDx: Psoriasis (early MF notoriously mimics), atopic dermatitis, parapsoriasis, contact dermatitis.

Treatment:

Stage IA/IB: NBUVB, topical steroids, topical nitrogen mustard (mechlorethamine), bexarotene gel
Stage IIB–III: PUVA ± interferon-α, bexarotene 300 mg/m²/day (oral retinoid)
Advanced: Extracorporeal photopheresis (ECP), vorinostat (HDAC inhibitor), mogamulizumab, romidepsin
Sézary: ECP + interferon + NBUVB

Contraindications: Systemic chemotherapy generally avoided in early stages (does not improve survival). Bexarotene — hypothyroidism risk (monitor TFTs), teratogenic.

34. LEPROSY (HANSEN'S DISEASE)

Findings: Hypopigmented or erythematous patches with LOSS OF SENSATION (key distinguishing feature), peripheral nerve thickening (ulnar, peroneal, great auricular, radial cutaneous), muscle wasting, claw hand, foot drop, facial disfigurement. Tuberculoid (TT): few lesions, strong immunity; Lepromatous (LL): numerous lesions, poor immunity, leonine facies, madarosis.

Investigations: Slit skin smear (acid-fast bacilli — Ziehl-Neelsen), biopsy (granulomas, nerve involvement), Lepromin test (Mitsuda reaction — positive in TT, negative in LL), nerve conduction study, PCR for M. leprae.

DDx: Tinea versicolor (no sensory loss), vitiligo (no sensory loss, no nerves), granuloma annulare, cutaneous sarcoidosis, lupus vulgaris.

OPD Rx (WHO Multidrug Therapy — MDT):

Paucibacillary (TT/BT, 1–5 patches): Dapsone 100 mg/day + Rifampicin 600 mg/month × 6 months
Multibacillary (BL/LL, >5 patches): Dapsone 100 mg/day + Clofazimine 50 mg/day + Rifampicin 600 mg/month + Clofazimine 300 mg/month × 12 months
Reactions:
- Type 1 (reversal): Prednisolone 40 mg/day (for nerve involvement — prevent disability)
- Type 2 (ENL): Thalidomide 100–400 mg/day (males only) or prednisolone

Contraindications: Thalidomide — females of childbearing age (devastating teratogen). Dapsone — G6PD deficiency.

35. LUPUS ERYTHEMATOSUS (CUTANEOUS)

Findings: ACLE (Acute Cutaneous LE): butterfly malar rash (spares nasolabial folds), photosensitivity. SCLE: annular/psoriasiform lesions on sun-exposed skin. DLE (Discoid LE): scarring, hypopigmented centre, hyperpigmented rim, follicular plugging, atrophy.

Investigations: ANA (sensitive, not specific), anti-dsDNA (specific for SLE), anti-Smith, complement C3/C4, CBC (cytopenia), urine protein/creatinine, skin biopsy with DIF (granular IgG/IgM/C3 at BMZ — "lupus band test"), anti-Ro/La (SCLE), antiphospholipid antibodies.

DDx: Rosacea (malar rash — but not photosensitive + telangiectasia), seborrhoeic dermatitis, dermatomyositis (heliotrope rash), tinea faciei, polymorphous light eruption.

OPD Rx:

Sun protection (SPF 50+, UVA + UVB)
Hydroxychloroquine 200–400 mg/day (first-line for all LE, reduces flares, protects organs)
Topical: Tacrolimus or clobetasol for DLE
Thalidomide 50–200 mg/day (refractory DLE/SCLE)
Systemic LE: Follow EULAR/ACR SLE guidelines (belimumab, anifrolumab)

Contraindications: Hydroxychloroquine — retinal toxicity with prolonged use (annual ophthalmology review mandatory). G6PD deficiency + dapsone (if used). Avoid drugs that trigger drug-induced lupus (hydralazine, procainamide, minocycline, anti-TNF).

36. DERMATOMYOSITIS

Findings: Heliotrope rash (periorbital violaceous discolouration + oedema), Gottron's papules (flat-topped purple papules on knuckles — PATHOGNOMONIC), V-sign, shawl sign, dilated nailfold capillaries, Mechanic's hands. Associated malignancy (especially in adults >40 yrs): ovarian, lung, colorectal, nasopharyngeal.

Investigations: Serum CK (elevated), aldolase, LDH, AST. Myositis-specific antibodies (anti-Jo-1/anti-MDA5/anti-TIF1γ — anti-TIF1γ: malignancy-associated). EMG (myopathic), MRI muscle, skin/muscle biopsy, PET-CT / full malignancy screen (gastroscopy, colonoscopy, CT, mammography).

DDx: SLE, systemic sclerosis, polymyositis, lichen planus, tinea faciei.

OPD Rx:

Prednisolone 1–1.5 mg/kg/day with slow taper
Methotrexate 15–25 mg/week (skin + muscle)
Azathioprine 2–3 mg/kg/day (myositis)
IVIG 2 g/kg/cycle every 4 weeks (skin-dominant/refractory: FDA approved)
Hydroxychloroquine (skin manifestations)
Sun protection mandatory

Contraindications: Methotrexate — hepatic disease, renal impairment, active infection, pregnancy. IVIG — IgA deficiency (anaphylaxis).

37. SYSTEMIC SCLEROSIS (SCLERODERMA)

Cutaneous Findings: Raynaud's phenomenon (first symptom), puffiness/swelling of fingers (early), then tight/bound-down skin (sclerodactyly), digital ulcers, telangiectasia, calcinosis cutis, hypopigmentation/hyperpigmentation ("salt and pepper"), salt-and-pepper hair, beaked nose, restricted oral aperture (microstomia).

Investigations: ANA, anti-centromere antibody (limited/CREST), anti-topoisomerase I/Scl-70 (diffuse, poor prognosis), anti-RNA polymerase III (renal crisis risk), nailfold capillaroscopy (giant loops, avascular areas), PFTs (ILD), echocardiogram (PAH), barium swallow/oesophageal manometry, renal function.

DDx: Mixed connective tissue disease, overlap syndrome, morphoea (localised scleroderma), eosinophilic fasciitis.

Treatment:

Raynaud's: Nifedipine 10–20 mg TDS, sildenafil, bosentan (digital ulcer prevention)
Skin fibrosis: Methotrexate (dcSSc), mycophenolate mofetil
ILD: Mycophenolate mofetil 3 g/day, nintedanib (pirfenidone alternative)
PAH: Bosentan, macitentan, sildenafil, riociguat, prostacyclin (IV epoprostenol)
Renal crisis: ACE inhibitor (captopril) URGENTLY — dialysis if needed

Contraindications in SSc: ACE inhibitors as general anti-hypertensive (increase renal crisis risk) but ARE the treatment for renal crisis. D-penicillamine — historically used, now largely abandoned. Steroids >15 mg/day — risk of renal crisis in diffuse SSc.

38. ACNE ROSACEA (already covered separately as #5) — PERIORAL DERMATITIS

Findings: Papulopustules around mouth (perioral sparing/zone around lips), chin, nasolabial folds, due to chronic topical steroid use (steroid-induced rosacea), fluorinated toothpaste.

OPD Rx:

STOP topical steroid (gradual if needed to avoid rebound — stepdown to hydrocortisone 1%, then stop)
Metronidazole 0.75% gel BD or topical erythromycin 2%
Oral doxycycline 100 mg OD × 6–12 weeks
Azelaic acid 15% gel BD (maintenance)

39. KAPOSI'S SARCOMA

Findings: Violaceous/purple patches, plaques, nodules on skin and mucosae. Starts as pigmented macules; disseminates. Four types: Classic (elderly men, lower limbs), Endemic (Africa), Iatrogenic (transplant), AIDS-related (widespread, fulminant). Associated HHV-8.

Investigations: Skin biopsy (spindle cells, slit-like vascular channels, plasma cells — HHV-8 immunostaining), HIV test and CD4 count, LDH, chest X-ray, endoscopy (GI involvement), CT staging.

DDx: Bacillary angiomatosis (HIV, Bartonella — similar appearance), haematoma, purpura, haemangioma, melanoma.

Treatment:

AIDS-related KS: START antiretroviral therapy (cART) — immune reconstitution controls KS
Localised: Intralesional vinblastine 0.1 mg/cm², cryotherapy, radiotherapy
Disseminated/visceral: Liposomal doxorubicin 20 mg/m² IV q3 weeks (first-line chemotherapy)
Paclitaxel (second-line)
Classic KS: Radiotherapy (excellent response)

Contraindications: Immunosuppression increases KS — reduce immunosuppression in transplant patients.

40. PYODERMA GANGRENOSUM (PG)

Findings: Rapidly evolving painful ulcer with undermined violaceous edge and necrotic base, typically on lower legs. PATHERGY phenomenon (new ulcers at trauma sites). Associated conditions: IBD (Crohn's/UC — 50%), rheumatoid arthritis, haematological malignancy (IgA paraproteinaemia), myeloid disorders.

Investigations: Biopsy from EDGE (neutrophilic infiltrate, exclude other diagnoses — it is a diagnosis of exclusion!). Wound culture (secondary infection). Colonoscopy/colonoscopy (IBD), protein electrophoresis (SPEP/UPEP), CBC, ANA, RF, ANCA. Pathergy test.

DDx: Vasculitis, necrotising fasciitis, venous/ischaemic ulcers, ecthyma, squamous cell carcinoma in ulcer.

OPD/Hospital Rx:

AVOID debridement (pathergy — will worsen!)
First-line: Cyclosporine 3–5 mg/kg/day OR prednisolone 0.5–1 mg/kg/day
Topical: Tacrolimus 0.1% ointment or potent steroid under occlusion
Biologic: Infliximab 5 mg/kg IV (especially if associated IBD — very effective); adalimumab
Wound care: Non-adherent, moisture-retaining dressings
Treat underlying disease (IBD therapy often controls PG)

Contraindications: SURGICAL DEBRIDEMENT (absolute contraindication — causes pathergy). Do NOT aggressively debride. Infliximab — active TB (screen IGRA/TST), active infections, decompensated heart failure.

ICU (extensive/rapidly progressive PG):

IV methylprednisolone 1 g/day × 3 days
IV cyclosporine 3–4 mg/kg/day
IV infliximab infusion
Wound management in ICU
Monitor for sepsis (large open wounds = infection risk)
Pain management (IV opioids — extremely painful)
Monitor renal function (cyclosporine nephrotoxicity)

QUICK REFERENCE SUMMARY TABLE

#	Disease	Key Finding	Gold Standard Investigation	First-Line Treatment	Key Contraindication
1	Atopic Dermatitis	Pruritus + flexural lichenification	Serum IgE + SCORAD	Emollients + topical steroids	Fluorinated steroids on face
2	Contact Dermatitis	Site-specific dermatitis	Patch test	Avoid allergen + topical steroids	Systemic steroids in DM
3	Psoriasis	Silvery plaques + Auspitz sign	Biopsy (Munro microabscesses)	Coal tar/NBUVB/methotrexate	MTX in pregnancy/liver disease
4	Acne Vulgaris	Comedones + papulopustules	Clinical ± hormonal screen	Benzoyl peroxide + adapalene	Isotretinoin in pregnancy
5	Rosacea	Centrofacial erythema without comedones	Clinical	Topical metronidazole + doxycycline	Topical steroids
6	Urticaria	Transient wheals	None (clinical) / IgE panel	Non-sedating antihistamines	Sedating AH in elderly
7	Scabies	Nocturnal pruritus + burrows	KOH/dermoscopy	Permethrin 5%	Ivermectin in pregnancy
8	Tinea	Annular scaly plaque	KOH + culture	Terbinafine cream/tablets	Terbinafine in liver disease
9	Candidiasis	Satellite pustules in folds	KOH (pseudohyphae)	Clotrimazole / fluconazole	Fluconazole in pregnancy
10	HSV	Grouped vesicles → ulcers	PCR (gold standard)	Aciclovir/valaciclovir	Aciclovir: reduce dose in renal failure
11	Herpes Zoster	Dermatomal vesicles	Clinical/PCR	Valaciclovir 1g TDS × 7 days	Live vaccine in immunocompromised
12	Impetigo	Honey-coloured crust	Wound swab	Mupirocin / flucloxacillin	Steroids in SSSS
13	Cellulitis	Poorly demarcated warm erythema	Clinical/blood cultures	Cefalexin / IV flucloxacillin	Debridement without NF confirmation
14	Varicella	Dewdrop on rose petal + crops	Clinical/PCR	Supportive ± aciclovir	Aspirin (Reye syndrome)
15	Molluscum	Umbilicated papules	Clinical / biopsy (Henderson bodies)	Cryotherapy / imiquimod	–
16	Warts (HPV)	Exophytic with black dots	Clinical	Salicylic acid / cryotherapy	Podophyllin in pregnancy
17	Pemphigus Vulgaris	Flaccid bullae + Nikolsky+	Biopsy + DIF + anti-Dsg antibodies	Rituximab + prednisolone	NSAIDs/penicillamine
18	Bullous Pemphigoid	Tense bullae, elderly	Biopsy + DIF + anti-BP180	Topical clobetasol / doxycycline	Long-term systemic steroids in elderly
19	Dermatitis Herpetiformis	Pruritic papulovesicles, extensor	DIF (granular IgA)	Dapsone + gluten-free diet	Dapsone in G6PD deficiency
20	SJS/TEN	Sheet epidermal loss + SCORTEN	Biopsy (full-thickness necrosis)	STOP drug + ICU + cyclosporine	Steroids (controversial/avoided)
21	Fixed Drug Eruption	Same site each time	Provocation test	Stop drug + topical steroid	Re-challenge with drug
22	DRESS	Rash + fever + eosinophilia + organ involvement	HHV-6, eosinophilia, biopsy	Stop drug + prednisolone	Early steroid withdrawal
23	Melanoma	ABCDE asymmetric pigmented lesion	Excision biopsy + Breslow	Surgery ± immunotherapy/targeted	Immunotherapy in active autoimmune disease
24	BCC	Pearly telangiectatic papule	Biopsy	Excision / Mohs	Vismodegib in pregnancy
25	SCC	Keratotic ulcerating nodule	Excision biopsy	Wide excision / Mohs	Immunosuppression post-transplant
26	Vitiligo	Chalk-white depigmented macules	Wood's lamp + TFTs	NBUVB + tacrolimus	PUVA in children <12 yrs
27	Alopecia Areata	Patchy non-scarring hair loss	Trichoscopy/biopsy	Intralesional triamcinolone / baricitinib	Baricitinib in pregnancy/malignancy
28	Lichen Planus	6 P's + Wickham striae	Biopsy (band-like infiltrate)	Clobetasol + prednisolone	Acitretin in pregnancy
29	Seborrhoeic Dermatitis	Greasy scale on seborrhoeic areas	Clinical	Ketoconazole 2% shampoo/cream	Fluorinated steroids on face
30	Pityriasis Rosea	Herald patch + Christmas tree	VDRL (exclude syphilis)	Supportive + cetirizine	–
31	Pityriasis Versicolor	Hypo/hyperpigmented + scale	KOH (spaghetti + meatballs)	Selenium sulphide / ketoconazole	–
32	Erythroderma	>90% BSA erythema + scale	Biopsy × 3 + flow cytometry	Treat cause + ICU support	Identify/treat underlying cause first
33	Mycosis Fungoides	Patch→plaque→tumour	Biopsy + IHC + TCR clonality	NBUVB / bexarotene / mogamulizumab	Systemic chemo in early stages
34	Leprosy	Hypopigmented + sensory loss	Slit-skin smear + biopsy	WHO MDT (dapsone + rifampicin ± clofazimine)	Thalidomide in women of childbearing age
35	Lupus (Cutaneous)	Malar rash / DLE scarring	ANA, anti-dsDNA, DIF (lupus band)	Hydroxychloroquine + sun protection	Drugs triggering drug-induced lupus
36	Dermatomyositis	Gottron's papules + heliotrope rash	Anti-TIF1γ/Jo-1 + biopsy + PET-CT	Prednisolone + MTX + IVIG	MTX in pregnancy; malignancy screen mandatory
37	Systemic Sclerosis	Sclerodactyly + Raynaud's	Anti-Scl70, nailfold capillaroscopy, PFTs	MMF + nifedipine + bosentan	High-dose steroids in diffuse SSc (renal crisis risk)
38	Perioral Dermatitis	Perioral papulopustules	Clinical	Stop topical steroids + doxycycline	Topical steroids
39	Kaposi's Sarcoma	Violaceous lesions + HHV-8	Biopsy + HIV/CD4	cART ± liposomal doxorubicin	Immunosuppression
40	Pyoderma Gangrenosum	Painful undermined ulcer + pathergy	Biopsy (edge) + exclude other causes	Cyclosporine / prednisolone / infliximab	Surgical debridement (absolute contraindication)

KEY ABBREVIATIONS

NBUVB = Narrowband ultraviolet B phototherapy
PUVA = Psoralen + UVA
DIF = Direct immunofluorescence
BMZ = Basement membrane zone
BSA = Body surface area
TEN = Toxic epidermal necrolysis
SJS = Stevens-Johnson syndrome
CTCL = Cutaneous T-cell lymphoma
cART = Combination antiretroviral therapy
MTX = Methotrexate
MMF = Mycophenolate mofetil

*Sources: Andrews' Diseases of the Skin (Clinical Dermatology), Fitzpatrick's Dermatology (8th ed.), Dermatology 2-Volume Set 5e, Harrison's Principles of Internal Medicine 22E — available in the medical textbook library.*Your credits are exhausted. Your daily credits reset tomorrow, or you can purchase a top-up for more.

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