 section number eight in Harrison alteration in the skin chapter number 59, approached to the patient with skin disorder, number 60 eczema Surya infection, Common skin disorder, skin manifestation, 61 skin manifestation of internal C 62 me logically mediated skin disease, 6310 drug reaction, 64 photos, sensitivity and other actions to sunlight. Can you give me from the Harrison’s detailed way to remember and can you add base two so I can become the best doctor.
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Here is your complete, high-yield study guide for Harrison's Section 8 - Alterations in the Skin (Chapters 59-64), built from the actual text of Harrison's Principles of Internal Medicine 22E with mnemonics and memory anchors to help you become the best doctor.
HARRISON'S SECTION 8 - ALTERATIONS IN THE SKIN
Chapters 59-64: Complete Study Guide with Mnemonics
CHAPTER 59 - APPROACH TO THE PATIENT WITH A SKIN DISORDER
The Core Concept
"The largest organ is visible - that is BOTH an advantage and a trap."
The casual observer misses subtle findings. Train your eye like a microscopist.
Primary Lesion Types - Mnemonic: "MPPVBC - My Patients Present Very Bad Cases"
| Letter | Lesion | Key Fact |
|---|---|---|
| M | Macule | Flat color change <1 cm (freckle, café-au-lait) |
| P | Patch | Flat color change >1 cm (vitiligo) |
| P | Papule | Elevated solid <1 cm |
| V | Vesicle | Fluid-filled <1 cm (herpes, varicella) |
| B | Bulla | Fluid-filled >1 cm (pemphigoid) |
| C | Cyst | Encapsulated fluid/semi-solid |
Secondary Lesions - Mnemonic: "SCALE-F"
- S - Scale (psoriasis)
- C - Crust (impetigo)
- A - Atrophy (steroids)
- L - Lichenification (chronic eczema)
- E - Erosion (partial thickness loss)
- F - Fissure (hand eczema)
Diagnostic Techniques - Mnemonic: "KTW-D"
| Test | When to Use | What You See |
|---|---|---|
| K - KOH prep | Fungal infection suspected | Hyphae (dermatophytes), pseudohyphae (Candida), "spaghetti & meatballs" (tinea versicolor) |
| T - Tzanck smear | Herpes simplex / VZV | Multinucleated epithelial giant cells |
| W - Wood's lamp | Hypopigmentation, fungal (tinea capitis) | Coral-red fluorescence (erythrasma), blue-green (Microsporum) |
| D - Diascopy | Differentiate blanching vs non-blanching | Non-blanching = purpura/vasculitis |
Clinical pearl: Tzanck smear - take from an EARLY vesicle, NOT a pustule or crust. Scrape the BASE, not the roof.
History Taking in Skin Disease - "10-Point SOAP-TRACK"
- Site of onset and progression
- Onset timing (sudden vs gradual)
- Associated itching, burning, pain, numbness
- Periods of resolution
- Time of day symptoms worsen
- Received medications (OTC + Rx)
- Associated systemic symptoms (fever, arthralgias, malaise)
- Comorbid illness
- Known allergies
- Family history (especially melanoma, atopy, psoriasis, acne)
Melanoma vs Benign Nevus - The ABCDE Rule
- A - Asymmetry
- B - Border irregularity
- C - Color variegation (black, blue, brown, pink, white in ONE lesion)
- D - Diameter >6 mm
- E - Evolution (history of change, new pruritus or pain)
CHAPTER 60 - ECZEMA, PSORIASIS, INFECTIONS & COMMON SKIN DISORDERS
The Eczema Family - Mnemonic: "SCAN-ASS"
| Type | Key Memory Hook |
|---|---|
| S - Seborrheic | Scalp, face (nasolabial folds), ears - "where sebum flows" - treat with ketoconazole shampoo |
| C - Contact (Allergic/Irritant) | Hands + shape of rash = shape of exposure |
| A - Atopic | Young + triad: eczema + asthma + allergic rhinitis |
| N - Nummular | Coin-shaped plaques; looks like ringworm |
| A - Asteatotic | Elderly + winter + dry skin + "crazy paving" cracks = "winter itch" |
| S - Stasis | Legs + venous incompetence + medial ankle first |
| S - (Dyshidrotic) | Palms/soles/lateral digits - tiny vesicles - triggered by hot weather, metals |
Stasis Dermatitis vs Cellulitis - HIGH-YIELD CLINICAL PEARL
| Feature | Stasis Dermatitis | Cellulitis |
|---|---|---|
| Distribution | Bilateral/symmetric | Unilateral |
| Warmth/tenderness | Mild | Prominent |
| Associated varicosities | Yes | No |
| Fever | Absent | Usually present |
Memory anchor: "Stasis is Symmetric" - if both legs are red, think stasis first.
Psoriasis - Mnemonic: "PENIS" (types)
- P - Plaque (most common - silvery scale on extensor surfaces, scalp, elbows, knees)
- E - Erythrodermic (total body - life-threatening)
- N - Nail changes (pitting, onycholysis, oil spots)
- I - Inverse (intertriginous areas - groin, axilla - no scale because moist)
- S - Small plaque + Scalp + Sebopsoriasis variants
Auspitz sign: Pinpoint bleeding when scale removed (dilated capillary loops in dermal papillae).
Koebner phenomenon: Psoriasis appears at sites of trauma.
Psoriasis Treatment Ladder - "Topical-Light-Systemic"
- Topical: glucocorticoids, vitamin D analogs (calcipotriol), retinoids, tar
- Phototherapy: narrow-band UVB, PUVA
- Systemic: methotrexate, cyclosporine, acitretin
- Biologics: anti-TNF (etanercept, adalimumab), anti-IL-17 (secukinumab), anti-IL-23 (guselkumab)
Common Skin Infections - Mnemonic: "DISH-VW"
| Organism | Disease | Key Feature |
|---|---|---|
| D - Dermatophyte | Tinea | KOH shows hyphae; "spaghetti & meatballs" for tinea versicolor |
| I - Impetigo | Staph/Strep | Honey-colored crust; bullous type = Staph aureus toxin |
| S - Sporothrix | Sporotrichosis | Lymphocutaneous (sporotrichoid) pattern along lymphatics |
| H - HPV | Warts | Plantar warts endophytic; central keratinized core + pinpoint bleeding |
| V - VZV/HSV | Vesicular | Tzanck smear for diagnosis |
| W - (Candida) | Candidiasis | Satellite pustules, "thrush" in mouth, KOH shows pseudohyphae |
Warts by HPV Type - "619 Rules Cervix"
- HPV 6, 11 = anogenital warts (condyloma)
- HPV 16, 18 = cervical carcinoma + anogenital neoplasia
- Flat warts = verruca plana (face, arms, legs - shaving spreads them)
- Plantar warts = endophytic - pare to reveal pinpoint bleeding
CHAPTER 61 - SKIN MANIFESTATIONS OF INTERNAL DISEASE
The Core Concept
Every skin finding can be a window into systemic disease. Learn the pattern-to-disease link.
Papulosquamous Diseases with Systemic Associations - "PALS-R"
| Condition | Internal Association |
|---|---|
| P - Psoriasis | Psoriatic arthritis (5-20%), IBD, metabolic syndrome |
| A - Acanthosis nigricans | Insulin resistance, type 2 DM, occult malignancy (GI adenocarcinoma) |
| L - Lichen planus | Hepatitis C, primary biliary cholangitis |
| S - Seborrheic keratoses (Leser-Trelat sign) | Rapid increase in number = internal malignancy (GI, lymphoma) |
| R - Reactive (Reiter's) | Reactive arthritis: keratoderma blennorrhagica on palms/soles |
Erythroderma (Total Body Erythema) - "PSDEL"
Causes to remember:
- P - Psoriasis (most common cause)
- S - Seborrheic dermatitis
- D - Drug reaction
- E - Eczema
- L - Lymphoma (Sézary syndrome = Erythrodermic CTCL + atypical lymphocytes in blood)
Sézary syndrome = erythroderma + lymphadenopathy + Sézary cells (cerebriform nuclei) in circulation. This is the leukemic form of CTCL.
Telangiectasias Pattern - HIGH-YIELD TABLE
| Pattern | Disease |
|---|---|
| Linear (face, neck) | Acne rosacea, actinically damaged skin, carcinoid |
| Mat telangiectasias (polygonal, 2-7mm) | Scleroderma (systemic sclerosis) |
| Periungual/nailfold | Lupus, scleroderma, dermatomyositis (the "big 3" CTDs) |
| Poikiloderma (3-component: hypo+hyper pigment + atrophy + telangiectasia) | Dermatomyositis, mycosis fungoides, radiation |
| Spider angiomas | Liver disease, pregnancy, normal |
Memory tip: "MAT = Scleroderma" (mat telangiectasias are pathognomonic for systemic sclerosis)
Hyperpigmentation Causes - Mnemonic: "ADD HEMP"
- A - Addison's disease (diffuse + accentuated in creases, buccal mucosa)
- D - Drugs (minocycline, hydroxychloroquine, bleomycin, amiodarone)
- D - Deposits (hemochromatosis - bronze skin)
- H - Hemochromatosis
- E - Ectopic ACTH (Nelson syndrome)
- M - Malignancy (Acanthosis nigricans = paraneoplastic)
- P - Porphyria cutanea tarda
Alopecia Classification - Scarring vs Non-Scarring
Non-Scarring (follicle preserved - reversible)
"TAD-TP"
- T - Telogen effluvium (stress, postpartum, thyroid disease, nutritional deficiency)
- A - Androgenetic alopecia (male/female pattern)
- D - Drugs (anagen effluvium: chemo with anthracyclines; telogen effluvium: many drugs)
- T - Tinea capitis (children)
- P - Alopecia areata (autoimmune - exclamation mark hairs)
Scarring (follicle destroyed - irreversible)
"CLFD"
- C - Cutaneous lupus (discoid lesions)
- L - Lichen planus (frontal fibrosing alopecia)
- F - Folliculitis decalvans
- D - Dissecting cellulitis
Urticaria - The "P-SAC-SC" Framework
Physical urticarias:
- Dermographism - linear wheals from scratching/pressure (5% of population)
- Solar urticaria - within minutes of sun exposure; sign of erythropoietic protoporphyria
- Cold urticaria - associated with cryoglobulins; avoid cold swimming (syncope risk)
- Cholinergic - small wheals + large flares; triggered by heat, exercise, emotion
Memory tip: "Solar urticaria = protoporphyria" (the ONLY physical urticaria tied to a systemic disease besides cold urticaria with cryoglobulins)
CHAPTER 62 - IMMUNOLOGICALLY MEDIATED SKIN DISEASES
Bullous Diseases - Mnemonic: "PP-BEL" (Pemphigus-Pemphigoid-Blistering-Epidermolysis-Linear)
| Disease | Blister Level | Antigen | Key Feature |
|---|---|---|---|
| Pemphigus vulgaris | Intraepidermal (suprabasal) | Desmoglein 3 (+/- 1) | Flaccid bullae + Nikolsky sign (+) + mucous membrane involvement |
| Bullous pemphigoid | Subepidermal | BP180 (BPAG2), BP230 | Tense bullae in elderly; mucous membrane spared usually; Nikolsky (-) |
| Dermatitis herpetiformis | Subepidermal | Tissue transglutaminase | Intensely pruritic vesicles on elbows/knees/buttocks; associated with celiac disease (gluten-sensitive enteropathy) |
| Linear IgA disease | Subepidermal | BP180 ectodomain | "String of pearls" blisters; associated with vancomycin |
| Epidermolysis bullosa acquisita | Subepidermal | Type VII collagen | Trauma-induced blisters |
Key Nikolsky Sign Logic
- Nikolsky (+) = lateral pressure causes skin to slip/blister = intraepidermal cleavage (pemphigus)
- Nikolsky (-) = subepidermal diseases (pemphigoid)
- Also (+) in: SSSS (Staph scalded skin syndrome), TEN (toxic epidermal necrolysis)
Autoimmune Skin Disease Quick Hits
Lupus skin patterns - "DAC-SL":
- D - Discoid (chronic scarring plaques)
- A - Acute cutaneous (malar "butterfly" rash)
- C - Cutaneous vasculitis
- S - Subacute cutaneous lupus (anti-Ro/SSA - photosensitive annular lesions)
- L - Livedo reticularis
Dermatomyositis skin signs - "HGSP-N":
- H - Heliotrope rash (periorbital violaceous discoloration)
- G - Gottron papules (knuckle plaques)
- S - Shawl sign (upper back/shoulders)
- P - Periungual telangiectasias + ragged cuticles
- N - "Mechanic's hands" (hyperkeratotic lateral fingers, anti-MDA5/anti-Jo-1)
CHAPTER 63 - DRUG REACTIONS
The Most Common Drug-Skin Reaction Patterns - Mnemonic: "MUSE-TEN"
| Pattern | Typical Drugs | Key Feature |
|---|---|---|
| M - Morbilliform/exanthematous | Penicillin, ampicillin, sulfa, allopurinol | Most common drug reaction; measles-like rash; starts trunk spreads distally |
| U - Urticaria | Penicillin, NSAIDs, ACE inhibitors | IgE-mediated or direct mast cell degranulation |
| S - Stevens-Johnson Syndrome (SJS) | Sulfa, aromatic anticonvulsants, allopurinol, nevirapine | <10% BSA detachment; mucosal involvement; high morbidity |
| E - DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) | Aromatic anticonvulsants, allopurinol, sulfa, dapsone | Delayed 2-8 weeks; fever + lymphadenopathy + internal organ involvement |
| T - TEN (Toxic Epidermal Necrolysis) | Same as SJS | >30% BSA detachment; massive skin loss; mortality 30-50% |
SJS vs TEN: SJS = <10% BSA; SJS-TEN overlap = 10-30%; TEN = >30% BSA. Both have Nikolsky sign (+).
DRESS Syndrome - Mnemonic: "DRESS = Delayed, Rash, Eosinophilia, Systemic, Severe"
- Onset: 2-8 WEEKS after drug (not days - this is the key distinguishing point)
- Drugs: aromatic anticonvulsants (carbamazepine, phenytoin, phenobarbital), allopurinol, sulfa, dapsone, abacavir
- Internal organs: liver, kidneys, lungs, heart (myocarditis)
- Eosinophilia + atypical lymphocytosis
- HHV-6 reactivation seen
- Treatment: stop drug, systemic steroids
Fixed Drug Eruption - The Bizarre One
- Same spot every time the drug is given
- Round, dusky-red to violaceous plaque
- Leaves hyperpigmentation after healing
- Common drugs: tetracycline, NSAIDs, sulfa, phenolphthalein (laxatives)
Phototoxic Drug Reactions
Drugs that cause phototoxicity (not allergy - anyone can get it with enough drug + light):
"Some Drugs Cause Photosensitive HITS"
- S - Sulfonamides
- D - Doxycycline (and all tetracyclines)
- C - Chlorpromazine (phenothiazines)
- P - Psoralens (PUVA)
- H - Hydrochlorothiazide
- I - Isotretinoin / Ibuprofen (and other NSAIDs)
- T - Tetracyclines
- S - Sparfloxacin (fluoroquinolones)
CHAPTER 64 - PHOTOSENSITIVITY AND OTHER REACTIONS TO SUNLIGHT
UV Radiation - The Spectrum
| Type | Wavelength | Key Effect |
|---|---|---|
| UV-C | 200-290 nm | Filtered by ozone; most lethal but doesn't reach us |
| UV-B | 290-320 nm | Sunburn, skin cancer, vitamin D synthesis |
| UV-A | 320-400 nm | Photoaging, photosensitivity reactions, penetrates glass |
Memory tip: "UV-B = Burns and cancer; UV-A = Aging and Always present (through clouds and glass)"
Chromophores - What Absorbs UV in Skin
- Endogenous: nucleic acids, proteins, lipids, 7-dehydrocholesterol (pro-vitamin D)
- Porphyrins (exogenous to skin - from bloodstream): absorb at Soret band ~400 nm + 580-660 nm
Photosensitivity Disease Classification - Mnemonic: "GMPNI"
| Category | Examples |
|---|---|
| G - Genetic | Xeroderma pigmentosum (DNA repair defect), Porphyrias (CEP, EPP, PCT, VP) |
| M - Metabolic | Albinism, phenylketonuria, Hartnup disease, pellagra, kwashiorkor |
| P - Phototoxic | Drugs (tetracyclines, fluoroquinolones, NSAIDs, psoralens), plants, porphyria cutanea tarda |
| N - Neoplastic/degenerative | Photoaging, actinic keratosis, basal cell carcinoma, SCC, melanoma |
| I - Idiopathic | PMLE, actinic prurigo, hydroa vacciniforme, solar urticaria, chronic actinic dermatitis |
Polymorphous Light Eruption (PMLE) - The Most Common Photosensitivity
- Most common type of photosensitivity disease
- More common in women
- Pruritic erythematous papules/plaques on sun-exposed skin (dorsum of hands, forearm, upper trunk)
- Face is USUALLY LESS AFFECTED (paradox - because the face gets sun hardening)
- "Hardening" phenomenon: recurs in spring but fades with continued exposure
- Must differentiate from cutaneous lupus (histology + DIF + ANA)
Porphyrias and Skin - "PCT Blisters; EPP Burns"
| Porphyria | Skin Finding | Mechanism |
|---|---|---|
| PCT (Porphyria cutanea tarda) | Blisters + fragile skin on dorsum of hands + hyperpigmentation | Uroporphyrin I accumulation; UVA activation |
| EPP (Erythropoietic protoporphyria) | Burning pain + erythema within MINUTES of sun; pitted nose/hands; solar urticaria | Protoporphyrin IX + UVA/visible light |
| CEP (Congenital erythropoietic) | Severe blistering, mutilation, pink-red teeth (erythrodontia) | Earliest onset, most severe |
PCT triggers: alcohol, estrogens, hepatitis C, iron overload, HIV
Treatment of PCT: phlebotomy + hydroxychloroquine (reduces porphyrin absorption)
Xeroderma Pigmentosum (XP) - Memory Card
- Autosomal recessive - defective nucleotide excision repair of UV-induced photoproducts
- Skin looks prematurely photoaged: dry, leathery
- Skin cancer in the first 2 decades of life
- Neurological involvement in some subtypes
Photoaging vs Sun Protection
| Feature | Intrinsic aging | Photoaging |
|---|---|---|
| Driver | Genetic/time | UV-A primarily |
| Result | Fine wrinkles, laxity | Solar elastosis, deep wrinkles, mottled pigment, actinic keratoses |
| Mechanism | Normal senescence | Cross-linking + degradation of dermal matrix proteins + abnormal elastin accumulation |
Sun protection factor (SPF): The key is UVB protection. SPF 15 blocks ~93% UVB; SPF 30 blocks ~97%. No SPF fully blocks UV-A - need "broad spectrum" label.
Photodynamic Therapy (PDT) - High-Yield
- Uses porphyrin precursors: 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL)
- These are converted to protoporphyrins in skin
- Activated by light (blue light for thin actinic keratoses; red light for superficial BCCs - deeper penetration)
- Generates ROS - targets tumor cells selectively
- Used for: actinic keratoses, superficial BCCs, SCCs
Anatomical Clues to Photosensitivity (vs Contact Dermatitis)
Photosensitivity is ABSENT in these areas:
- Hairy scalp (hair shades)
- Upper eyelids
- Retroauricular areas
- Infranasal and submental regions
Contact dermatitis from airborne sensitizers can MIMIC photosensitivity by affecting similar exposed areas - but it also involves the shaded areas.
QUICK MASTER TABLE - "What Condition = What Skin Finding?"
| Skin Finding | Think of |
|---|---|
| Malar rash | SLE |
| Heliotrope + Gottron papules | Dermatomyositis |
| Mat telangiectasias | Scleroderma |
| Acanthosis nigricans | Insulin resistance / adenocarcinoma |
| Pyoderma gangrenosum | IBD (especially Crohn's), RA, hematologic malignancy |
| Erythema nodosum | Sarcoidosis, IBD, strep, TB, drugs |
| Palpable purpura | Small vessel vasculitis |
| Dermatitis herpetiformis | Celiac disease |
| Erythema chronicum migrans (bull's eye) | Lyme disease |
| Necrobiosis lipoidica | Diabetes mellitus |
| Solar urticaria | Erythropoietic protoporphyria |
| Nikolsky sign (+) | Pemphigus vulgaris, TEN, SSSS |
| Flaccid bullae + mucous membrane involvement | Pemphigus vulgaris |
| Tense bullae in elderly | Bullous pemphigoid |
| Intensely itchy vesicles on elbows/knees | Dermatitis herpetiformis = celiac |
| Fixed drug eruption (same spot) | Tetracycline, NSAIDs, sulfa |
| Delayed rash 2-8 weeks + eosinophilia + fever | DRESS syndrome |
| "String of pearls" blisters + vancomycin | Linear IgA disease |
THE ULTIMATE "BASE-2" MEMORY SYSTEM
The two most clinically important contrasts to cement in your mind:
1. Blister Level Tells Everything
- Intraepidermal = Nikolsky (+), flaccid, mucous membranes = PEMPHIGUS
- Subepidermal = Nikolsky (-), tense, elderly = PEMPHIGOID
2. Drug Reaction Timing Tells Everything
- Hours-days = urticaria, morbilliform, phototoxic, fixed
- 2-8 weeks = DRESS (this is the exam trap - students think "drug rash" = fast onset)
- Days-weeks = SJS/TEN
ONE-PAGE VISUAL ANCHOR FOR ALL 6 CHAPTERS
SKIN EXAMINATION FLOWCHART
Is the lesion FLAT or RAISED?
FLAT = macule/patch → think pigment disorder, vascular
RAISED = papule/plaque/nodule → think inflammation, neoplasm
Does it SCALE?
YES = papulosquamous → Psoriasis, Lichen planus, Tinea, CTCL
NO → Vesicle? → Herpes/pemphigus/varicella
→ Wheal? → Urticaria
→ Purpura? → Vasculitis
Is there MUCOSAL involvement?
YES → Pemphigus vulgaris, SJS/TEN, EM major, Lichen planus
Is the eruption in SUN-EXPOSED areas?
YES → Photosensitivity, lupus, PMLE, phototoxic drug reaction
Is it DRUG-related?
Immediate = urticaria/anaphylaxis
Days = morbilliform
Weeks = DRESS
Same spot every time = fixed drug eruption
All content sourced directly from Harrison's Principles of Internal Medicine, 22nd Edition (2025), Section 8: Alterations in the Skin, Chapters 59-64 - Harrison's Principles of Internal Medicine 22E, pp. 398-553.
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