Approach to a child with fever and rash in 10marks format for 3rd yr dermatology post graduate theory examination

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fever rash child maculopapular exanthem differential diagnosis

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Approach to a Child with Fever and Rash

Introduction (0.5 marks)

Fever with rash in a child is a common yet diagnostically challenging presentation. It spans a wide spectrum from benign self-limiting viral exanthems to life-threatening emergencies (meningococcaemia, toxic shock syndrome). A systematic approach — combining a detailed history, morphological characterisation of the rash, and targeted investigations — is essential for accurate diagnosis and timely management.

I. History (1.5 marks)

A. Fever Details

Onset, duration, pattern (continuous, remittent, intermittent)
Height of fever: very high (>40°C) suggests bacterial sepsis or Kawasaki disease
Relation to rash: Did the rash appear with fever or after defervescence?
- Rash appears after fever subsides → Roseola infantum (HHV-6)
- Rash appears with fever → measles, rubella, scarlet fever, dengue

B. Rash Details

Onset, site of onset, direction of spread (cephalocaudal, centrifugal)
Evolution (fixed vs. migratory), pruritus, desquamation

C. Associated Symptoms

System	Clues
URTI (3 Cs)	Cough, coryza, conjunctivitis → Measles
Sore throat, strawberry tongue	Scarlet fever
Lymphadenopathy (postauricular/occipital)	Rubella
Arthralgia, retro-orbital pain	Dengue
Red eyes, cracked lips, swollen hands	Kawasaki disease
Headache, neck stiffness, photophobia	Meningococcal meningitis
Slapped-cheek appearance	Erythema infectiosum (Fifth disease)

D. Epidemiological History

Vaccination status (MMR, varicella)
Contact with ill individuals, outbreaks
Travel history (dengue-endemic areas)
Drug history (drug hypersensitivity rash mimics viral exanthems)
Insect/tick bites (Rocky Mountain spotted fever, rickettsial diseases)

II. Examination (2 marks)

A. General Assessment

Toxic vs. non-toxic appearance: toxic child = bacterial sepsis; well-appearing = viral exanthem
Vital signs: BP (hypotension → septic shock), pulse, temperature
Assess for signs of systemic compromise: altered sensorium, poor perfusion, petechiae with fever = emergency

B. Morphological Classification of Rash

Morphology	Key Diagnoses
Maculopapular (blanching)	Measles, rubella, roseola, drug rash, dengue
Vesicular/bullous	Varicella, herpes zoster, HSV, hand-foot-mouth (HFMD)
Petechial/Purpuric (non-blanching)	Meningococcaemia, ITP, HSP (IgAV), rickettsial
Urticarial	Drug hypersensitivity, viral, serum sickness
Desquamating/Scarlatiniform	Scarlet fever, Kawasaki, SSSS, TSS
Target lesions	Erythema multiforme, Stevens-Johnson syndrome

The glass tumbler test (blanching): A non-blanching petechial/purpuric rash + fever = meningococcal disease until proved otherwise — treat empirically.

C. Distribution of Rash

Pattern	Diagnosis
Starts at hairline → spreads cephalocaudal	Measles (rubeola)
Face first → trunk → limbs; fades in 3 days	Rubella
Trunk → spreads peripherally after defervescence	Roseola
"Slapped cheeks" + lacy reticular rash on limbs	Erythema infectiosum (B19)
Palms, soles, oral mucosa	HFMD, Rocky Mountain spotted fever, secondary syphilis
Acral (hands, feet, periungual)	Kawasaki disease

D. Enanthem (Oral Mucosa)

Koplik's spots (white spots on buccal mucosa opposite lower molars) → Pathognomonic of measles
Strawberry tongue → Scarlet fever, Kawasaki disease
Oral vesicles/ulcers → HFMD (Coxsackievirus A16), herpangina

E. Other Examination Findings

Lymphadenopathy: cervical (measles, KD, mono), postauricular/occipital (rubella), generalised (EBV, HIV)
Eye changes: conjunctival injection (KD, measles); uveitis (JIA)
Hepatosplenomegaly: EBV, dengue, typhoid
Meningism: Neisseria meningitidis, viral meningitis
Joint swelling: HSP, reactive arthritis, rheumatic fever
Desquamation of fingertips (1–2 weeks later): Kawasaki, SSSS, scarlet fever

III. Classification: Fever-Rash Timing

Pattern	Disease
Fever → Rash (simultaneous)	Measles, rubella, scarlet fever, dengue, rickettsia
Fever → Defervescence → Rash	Roseola (HHV-6)
Rash before fever	Drug eruption
Fever + non-blanching rash = EMERGENCY	Meningococcaemia, HSP with sepsis

IV. Differential Diagnosis by Aetiology (1 mark)

Viral

Disease	Pathogen	Rash Type
Measles	Paramyxovirus	Maculopapular, cephalocaudal
Rubella	Togavirus	Maculopapular, fades in 3 days
Roseola (6th disease)	HHV-6/7	Macular, post-defervescence
Erythema infectiosum (5th disease)	Parvovirus B19	Slapped-cheek, reticular lacy
Varicella	VZV	Pleomorphic vesicular (dew drops on rose petal)
HFMD	Coxsackievirus A	Vesicles on palms, soles, oropharynx
Dengue	Flavivirus	Islands of white in sea of red

Bacterial

Disease	Organism	Rash Type
Scarlet fever	Group A Streptococcus	Sandpaper, pastia lines, perioral pallor
Meningococcaemia	Neisseria meningitidis	Petechial → purpuric → purpura fulminans
SSSS	S. aureus (exfoliative toxin)	Superficial bullae, Nikolsky sign +
Rickettsial	Rickettsia spp.	Petechial, centripetal (palms/soles)

Other

Kawasaki disease: Fever >5 days + ≥4 of 5 criteria (conjunctival injection, oral changes, rash, lymphadenopathy, extremity changes)
HSP (IgA vasculitis): Palpable purpura on buttocks/extensor limbs + arthritis + abdominal pain + nephritis
Drug hypersensitivity: Maculopapular, 7–10 days after first dose; pruritic; drug history essential
SJS/TEN: Target lesions, mucosal involvement, epidermal detachment

V. Investigations (1.5 marks)

Investigation	Purpose
CBC with differential	Leucocytosis (bacterial), leucopenia (viral/dengue), thrombocytopenia (dengue, ITP)
Blood culture	Bacterial sepsis
CRP, ESR, Procalcitonin	Sepsis biomarkers
NS1 antigen, dengue IgM/IgG	Dengue
Serology (IgM/IgG)	Measles, rubella, EBV, CMV, parvovirus B19
Throat swab + RADT	Group A Strep (scarlet fever)
Paul-Bunnell / Monospot	Infectious mononucleosis
Tzanck smear, Viral swab PCR	Varicella, HSV
Urine analysis	HSP nephritis, KD
ECHO, ECG	Kawasaki disease (coronary artery aneurysm screening)
CSF analysis	Meningococcal/viral meningitis
Widal, Blood culture	Typhoid (rose spots)
Skin biopsy	If diagnosis uncertain (vasculitis, SJS)

VI. Management Principles (1.5 marks)

A. Emergency Red Flags → Immediate Action

Non-blanching petechiae/purpura + fever: IV Ceftriaxone 100 mg/kg stat → admit ICU
Toxic-appearing child: secure IV access, blood cultures, empirical antibiotics
Suspected SJS/TEN: stop all drugs, admit, ophthalmology, dermatology, ICU

B. Disease-Specific Treatment

Condition	Treatment
Measles	Supportive; Vitamin A (WHO protocol)
Varicella	Oral acyclovir (immunocompromised: IV); avoid salicylates (Reye's)
Scarlet fever	Penicillin V/amoxicillin ×10 days
Meningococcaemia	IV Ceftriaxone; prophylaxis contacts (rifampicin)
Kawasaki disease	IVIG 2 g/kg single dose + Aspirin; follow-up ECHO
Dengue	Supportive; monitor platelets, haematocrit
SSSS	IV anti-staphylococcal antibiotics; wound care
Drug eruption	Withdraw offending drug; antihistamines; steroids if severe
HSP (IgA vasculitis)	NSAIDs; steroids for severe abdominal/renal involvement

C. General Supportive Care

Antipyretics (paracetamol/ibuprofen)
Adequate oral/IV hydration
Isolation precautions as appropriate (airborne: measles/varicella; droplet: meningococcal)
Notification to public health authorities for notifiable diseases (measles, meningococcal)

VII. A Practical Algorithm (0.5 marks)

FEVER + RASH in a Child
        │
        ├── Non-blanching (petechial/purpuric)?
        │          └── YES → EMERGENCY: rule out meningococcaemia
        │
        ├── Blanching maculopapular?
        │          ├── Koplik's spots → Measles
        │          ├── Post-defervescence → Roseola
        │          ├── Postauricular LN + faint rash → Rubella
        │          ├── Slapped cheeks → Erythema infectiosum (B19)
        │          ├── Sandpaper + strawberry tongue → Scarlet fever
        │          └── Island of white + thrombocytopenia → Dengue
        │
        ├── Vesicular?
        │          ├── Dew drops on rose petal → Varicella
        │          └── Palms + soles + mouth → HFMD
        │
        └── Fever >5 days + ≥4 criteria → Kawasaki disease

Conclusion (0.5 marks)

A meticulous history and rash morphology are the cornerstones of diagnosis. The single most critical discriminator is blanching vs. non-blanching: non-blanching purpura with fever mandates emergency treatment for meningococcaemia. Vaccination status, enanthem, timing of rash relative to fever, and systemic features help narrow the differential. Investigations should be targeted and treatment must be disease-specific with appropriate isolation, contact tracing, and public health notification.

References:

Tintinalli's Emergency Medicine, Chapters 12 & 142 (Viral Exanthems, Kawasaki Disease)
Red Book 2021: Report of the Committee on Infectious Diseases (AAP) — Kawasaki Disease, Meningococcal Infections
Harrison's Principles of Internal Medicine, 22nd Ed. — Meningococcal Disease
Fitzpatrick's Dermatology, 9th Ed. — Petechial/Purpuric Rashes
Sherris & Ryan's Medical Microbiology, 8th Ed. — Roseola, Exanthems

Illustrative images for reference:

Measles maculopapular exanthem — cephalocaudal spread

Measles: erythematous maculopapular rash beginning at hairline, spreading cephalocaudally, with coalescence

Scarlet fever: diffuse sandpaper-like erythematous blanching rash; note uniform distribution

Rubella: discrete pink maculopapular lesions; rapid spread; fades by day 3; postauricular lymphadenopathy is characteristic

Dengue: confluent erythema with characteristic "islands of white in a sea of red"

Enumerate Neutrophillic dermatoses .Discuss pyoderma gangrenosum in 10marks format for 3rd yr dermatology post graduate theory examination

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Neutrophilic Dermatoses — Enumeration & Pyoderma Gangrenosum

PART A: Enumeration of Neutrophilic Dermatoses (2 marks)

Neutrophilic dermatoses are a group of inflammatory skin conditions characterised histologically by a sterile, non-infectious neutrophilic infiltrate in the skin (epidermis, dermis, or subcutaneous tissue), without primary vasculitis or infection.

Classification

I. Classic Neutrophilic Dermatoses

Sweet Syndrome (Acute febrile neutrophilic dermatosis) — Dermal neutrophilic infiltrate
Pyoderma Gangrenosum (PG) — Neutrophilic ulcerating dermatosis
Behçet Disease — Neutrophilic vasculitis + systemic involvement
Bowel-Associated Dermatosis-Arthritis Syndrome (BADAS)
Rheumatoid Neutrophilic Dermatitis
Subcorneal Pustular Dermatosis (Sneddon-Wilkinson disease)
IgA Pemphigus (Intraepidermal neutrophilic type)

II. Neutrophilic Dermatoses Associated with Hematologic Malignancies 8. Bullous PG / Bullous Sweet Syndrome 9. Neutrophilic eccrine hidradenitis 10. Histiocytoid Sweet syndrome

III. Neutrophilic Dermatoses Associated with Bowel Disease 11. Pustular psoriasis 12. Pyostomatitis vegetans

IV. Autoinflammatory Syndromes with Neutrophilic Skin Involvement 13. PAPA syndrome (Pyogenic Arthritis, PG, Acne) 14. PASH syndrome (PG, Acne, Suppurative Hidradenitis) 15. PAPASH syndrome 16. SAPHO syndrome

V. Others 17. Erythema elevatum diutinum 18. Acute generalized exanthematous pustulosis (AGEP) 19. Blastomycosis-like pyoderma 20. Reactive arthritis–associated neutrophilic dermatosis

PART B: Pyoderma Gangrenosum (PG) in Detail (8 marks)

1. Definition & Historical Note

Pyoderma gangrenosum is a rare, painful, recurrent, ulcerating neutrophilic dermatosis associated with systemic disease in ~50% of patients. The name is a misnomer — it is neither pyogenic in aetiology nor truly gangrenous.

First described by Brocq (1908) as "geometric phagedism"
Term coined by Brunsting, Goeckerman & O'Leary (1930)

2. Epidemiology

Incidence: ~3–10 cases/million/year
Affects all ages; peak incidence in the 4th–6th decade
Female predominance in classic form
~4% of cases occur in children (>40% have underlying IBD; 18% have leukemia)
~25–50% of cases are idiopathic

3. Pathogenesis

PG is believed to result from dysregulation of innate immunity rather than primary infection. Key mechanisms include:

Pathway	Role
IL-1β overexpression	Central driver; canakinumab (anti-IL-1β) effective clinically
IL-8, IL-17, TNF overexpression	Found in lesional skin biopsies
Th1/Th17 pathway	IL-23 and JAK/STAT pathway implicated
Pathergy	IL-8 and IL-36 overexpression trigger lesions at trauma sites
PTPN6 splice variants	Murine model data; links to Sweet syndrome spectrum
Autoinflammatory genes	PAPA, PASH syndromes — aberrant inflammasome activation

Pathergy (development of lesions at sites of minor trauma) occurs in 20–30% of patients — surgeons must be warned; avoid unnecessary debridement.

4. Clinical Features

A. Primary Lesion

Begins as a painful inflammatory pustule on erythematous/violaceous base
Rapidly ulcerates and expands

B. Classic/Fully Developed Lesion (Ulcerative PG)

Deeply painful ulcer with:
- Undermined, overhanging, violaceous/gray-purple borders ← pathognomonic sign
- Surrounding erythematous halo
- Purulent or vegetative base
Most common on lower extremities (pretibial area) and trunk
Heals with characteristic cribriform (sieve-like) atrophic scars
Satellite violaceous papules may appear peripherally and fuse ("cheesecloth" pattern early on)

PG ulcer with violaceous undermined border

Classic PG: deep ulcer with undermined violaceous border, purulent base, and surrounding erythema

5. Clinical Variants

Variant	Features	Associated Condition
Ulcerative (Classic)	Painful, deep, undermined violet-bordered ulcer; lower limbs	IBD, RA
Bullous (Atypical)	Superficial blue-gray bullae; dorsal hands and face; overlaps with bullous Sweet syndrome	AML, MDS, IgA gammopathy
Pustular	Multiple sterile pustules; rarely ulcerate; resolve without scar	IBD, Behçet
Vegetative (Superficial granulomatous)	Superficial, slowly enlarging, cribriform ulceration; verrucous border; trunk; least aggressive	Often no systemic disease
Peristomal PG	Around surgical stomas; erosions and ulcers	Post-colectomy, IBD
Postsurgical PG	At surgical wounds; misdiagnosed as necrotising fasciitis	Post-breast surgery, etc.
Mucosal (Pyostomatitis vegetans)	Labial/buccal mucosa; vegetative plaques studded with pustules	IBD

6. Associated Systemic Conditions (50% of cases)

Category	Specific Diseases
Inflammatory bowel disease (most common)	Ulcerative colitis > Crohn's disease (1.5–5% of IBD patients)
Arthritis	Seronegative/seropositive RA, axial arthropathy
Hematologic disorders	AML, CML, CLL, MDS, IgA monoclonal gammopathy, myeloma, polycythemia vera
Autoinflammatory syndromes	PAPA, PASH, PAPASH, SAPHO
Other	Sarcoidosis, SLE, thyroid disease, HIV

IBD is more common in patients <65 years; malignancy more common >65 years — Dermatology 2-Volume Set 5e

7. Histopathology

PG has no pathognomonic histology — biopsy is primarily used to exclude mimics.

Stage	Histological Findings
Early lesion	Suppurative folliculitis; follicular rupture
Active expanding lesion	Massive dermal oedema; neutrophilic abscess; epidermal neutrophilic abscesses at violaceous border
Mature lesion	Fibrosing inflammation at ulcer edge
All stages	Sterile infiltrate (no organisms on culture/special stains); no primary vasculitis

Biopsy should be taken from the active, undermined edge and must include adequate depth (down to panniculus). Tissue must also be sent for bacterial, mycobacterial, fungal, and viral cultures.

8. Diagnosis

PG is a diagnosis of exclusion — no single specific serological or histological test exists.

Three Validated Diagnostic Criteria Systems:

Criteria	Requirements
Su Criteria	Both major criteria + ≥2 minor criteria
PARACELSUS Score	Score >10 points (progressive course + violaceous border + other features)
Delphi Consensus Criteria	Major criterion (biopsy with neutrophilic infiltrate) + ≥4/8 minor criteria

Su Criteria:

Major: (1) Rapid progression of painful necrolytic ulcer with irregular violaceous undermined border; (2) Other causes excluded
Minor: (1) Pathergy; (2) History of IBD/arthritis; (3) History of pustule/papule ulcerating within 4 weeks; (4) Cribriform scarring; (5) Response to systemic steroids or CSA; (6) Peripheral neutrophilia on biopsy

Investigations

Investigation	Purpose
Skin biopsy (edge + depth) + cultures	Exclude infection, tissue diagnosis
CBC, peripheral smear, bone marrow	Exclude haematological malignancy
Colonoscopy + stool occult blood	Evaluate for IBD
SPEP + immunofixation electrophoresis	IgA/IgG gammopathy
ANA, ANCA, antiphospholipid Ab, VDRL	Exclude vasculitis, autoimmune, syphilis
CXR, urinalysis	Screen for systemic disease

9. Differential Diagnosis

Early (non-ulcerative) stage:

Sweet syndrome, folliculitis, insect bite, panniculitis, Behçet disease, cellulitis, halogenoderma

Ulcerative stage (most important):

Category	Mimics
Vascular	Venous stasis ulcer, arterial occlusive disease, antiphospholipid syndrome
Vasculitis	Cutaneous PAN, ANCA vasculitis, SLE
Infection	Ecthyma gangrenosum, atypical mycobacteria, deep fungi (blastomycosis, sporotrichosis), leishmaniasis, amebiasis
Malignancy	SCC, cutaneous lymphoma, leukemia cutis
Other	Calciphylaxis, factitial disease, brown recluse spider bite, hydroxyurea ulcer

Critical warning: PG misdiagnosed as necrotising fasciitis → aggressive surgical debridement → pathergy → expansion of ulcer. Always consider PG before surgery on chronic ulcers.

10. Treatment

Key principle: Halt inflammation + promote wound healing. Treat underlying disease.

A. Local/Topical (mild/localised disease)

Treatment	Notes
Potent topical corticosteroids	First-line for solitary or slowly progressive lesions
Intralesional triamcinolone	Pathergy risk at injection sites
Topical tacrolimus 0.1%	Effective; monitor levels if large surface area
Topical timolol	Emerging evidence
Wound care	Occlusive dressings, whirlpool baths; avoid debridement

B. Systemic (moderate–severe disease)

Drug	Dose	Mechanism
Prednisolone (first-line)	1 mg/kg/day PO	Blocks IL-1α/β, impairs neutrophil migration
Cyclosporine (first-line)	3–5 mg/kg/day PO	Calcineurin inhibitor; reduces IL-2, TNF-α, IFN-γ
IV Methylprednisolone (very severe)	1 g/day × 3–5 days	Rapid induction
Dapsone	50–200 mg/day	Inhibits neutrophil myeloperoxidase; suppresses IL-8, TNF-α
Minocycline	100 mg BD	Suppresses neutrophil chemotaxis, MMP, cytokines
Mycophenolate mofetil	500 mg–1.5 g BD	Steroid-sparing; inhibits T/B cell proliferation
Azathioprine	2–2.5 mg/kg/day	Purine analogue; steroid-sparing
Methotrexate	Up to 30 mg/week	Folate antimetabolite; anti-neutrophil chemotaxis

C. Biologics (refractory disease)

Drug	Target	Notes
Infliximab (best evidence)	TNF-α	5 mg/kg IV at 0, 2, 6 weeks then 6–8 weekly; RCT evidence (MAPP trial)
Adalimumab	TNF-α	40 mg SC every 1–2 weeks
Canakinumab	IL-1β	Especially in autoinflammatory PG (PAPA, PASH)
Secukinumab/Ixekizumab	IL-17	Emerging data
Ustekinumab	IL-12/23	IBD-associated PG
Tofacitinib	JAK1/3	JAK-STAT pathway; refractory cases

D. Wound Care Principles

Avoid aggressive debridement — triggers pathergy
Moist wound environment; non-adherent dressings
Skin grafting only under adequate systemic immunosuppression

11. Prognosis

Variable — disease may remit, recur, or pursue a chronic course
Cribriform scarring is characteristic of healed lesions
Activity of PG and IBD may run independent courses — colectomy does not reliably cure PG
Reappearance of PG lesions in malignancy-associated cases may signal cancer relapse
Mortality directly from PG is rare; morbidity from associated systemic diseases is significant

PG — violaceous undermined ulcer on lower limb

PG: Large irregular ulcer with ragged violaceous undermined borders, erythematous halo, and granulating base — lower extremity

A: Localised PG on leg; B: Extensive abdominal PG in AML patient; C: Same lesion after 2 weeks of cyclosporine + prednisolone — healthy granulation tissue emerging

Summary Table — PG at a Glance

Feature	Details
Aetiology	Neutrophilic dysregulation; idiopathic in 25–50%
Primary lesion	Pustule → necrotic ulcer
Pathognomonic sign	Undermined violaceous border
Most common site	Lower limbs, pretibial
Most common association	Inflammatory bowel disease
Pathergy	20–30%
Biopsy	Sterile neutrophilic infiltrate; no vasculitis; exclude mimics
First-line systemic Rx	Prednisolone, cyclosporine
Best biologic evidence	Infliximab (MAPP trial)
Healing scar	Cribriform (sieve-like) atrophic scar

References:

Dermatology 2-Volume Set, 5th Ed. (Bolognia et al.) — Chapter 25: Pyoderma Gangrenosum, pp. 547–555
Andrews' Diseases of the Skin, 13th Ed. — Chapter 7: Reactive Neutrophilic Dermatoses, pp. 171–174
Fitzpatrick's Dermatology, 9th Ed. — Chapter 37: PG Differential Diagnosis & Treatment Tables
Dermatology 2-Volume Set, 5th Ed. — Table 25.8: PG Diagnostic Criteria (Su, PARACELSUS, Delphi Consensus)

Approach to a patient coming with pruritus in 10marks format for 3rd yr dermatology post graduate theory examination

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