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| Infantile acropustulosis of palms and soles -look for scabies |
🧭 Concise takeaway
These disorders fall into five mechanistic clusters:
Sterile neutrophilic dermatoses
Eosinophilic pustular disorders
Genodermatoses
Nutritional/metabolic dermatoses
Neonatal benign pustuloses
Understanding the cluster makes diagnosis far easier than memorising each entity.
🔬 1. Sterile neutrophilic pustular dermatoses
These are neutrophil‑driven, non‑infective, often associated with systemic inflammation.
Acropustulosis of Hallopeau (Pustular psoriasis variant) Chronic sterile pustules on fingertips/toes; nail destruction; linked to IL‑36 pathway dysregulation.
Subcorneal pustular dermatosis (Sneddon–Wilkinson) “Half‑half” pustules; superficial subcorneal neutrophils; associated with IgA paraproteinaemia.
Reiter’s syndrome (Reactive arthritis) – keratoderma blennorrhagicum Sterile pustules on palms/soles; histology resembles pustular psoriasis.
Sweet’s syndrome (Acute febrile neutrophilic dermatosis) Tender plaques with pseudovesiculation; dense neutrophils; associated with malignancy, IBD, drugs.
Pyoderma gangrenosum (pustular variant) Painful pustules → ulceration; neutrophilic infiltrate; pathergy; associated with IBD, arthritis, haematologic disease.
Erosive pustular dermatosis of the scalp Elderly; chronic erosions, crusts, sterile pustules; often post‑trauma; scarring alopecia.
Acne necrotica (necrotizing lymphocytic folliculitis) Middle‑aged adults; necrotic follicular papules on scalp/face; chronic relapsing; scarring.
🧬 2. Eosinophilic pustular disorders
Driven by eosinophilic folliculotropic inflammation.
Eosinophilic pustular folliculitis (Ofuji disease) Annular follicular pustules; intense pruritus; associated with HIV, infants, or drug reactions.
Incontinentia pigmenti (Stage 1) Neonatal vesiculopustular phase with eosinophils; X‑linked dominant (IKBKG mutation); progresses to verrucous → hyperpigmented → atrophic stages.
🧪 3. Nutritional / metabolic pustular dermatoses
These mimic infection but are metabolic.
Acrodermatitis enteropathica (Zinc deficiency) Acral/periorificial dermatitis with pustules; alopecia; diarrhoea; congenital (SLC39A4) or acquired.
Glucagonoma syndrome (Necrolytic migratory erythema) Erythematous plaques with superficial necrosis and pustules; intertriginous/acral; associated with diabetes, weight loss, glossitis.
👶 4. Benign neonatal pustuloses
Sterile, self‑resolving, important to distinguish from infection.
Transient neonatal pustular melanosis Present at birth; fragile pustules → collarettes → hyperpigmented macules; neutrophils.
Erythema toxicum neonatorum Day 2–3 onset; erythematous papules/pustules; eosinophils; sparing palms/soles.
🌿 5. Other inflammatory/infective‑mimicking pustular disorders
Not infectious but often mistaken for infection.
Tycoon scalp (Assuming you mean tycoon = tycosis / folliculitis decalvans variant) Chronic pustular folliculitis with scarring alopecia; neutrophilic.
Tuberculoid leprosy (pustular reactions) Rare; type 1 lepra reactions can produce sterile pustules; granulomatous histology.
🩺 Quick diagnostic table (clinically useful)
| Condition | Key clue | Histology | Association |
|---|---|---|---|
| Hallopeau | Fingertip pustules + nail loss | Neutrophils, psoriasiform | IL‑36 pathway |
| Subcorneal pustular dermatosis | “Half‑half” pustules | Subcorneal neutrophils | IgA gammopathy |
| Acrodermatitis enteropathica | Acral/periorificial | Pallor, parakeratosis | Zinc deficiency |
| Glucagonoma/NME | Migratory erythema | Necrolysis | Glucagonoma |
| Reiter’s | Keratoderma | Neutrophils | Reactive arthritis |
| Incontinentia pigmenti | Linear vesiculopustules | Eosinophils | IKBKG mutation |
| EPF | Follicular pustules | Eosinophils | HIV, infants |
| TNPM | At birth, hyperpigmented macules | Neutrophils | Benign |
| ETN | Day 2–3, eosinophils | Eosinophils | Benign |
| Sweet’s | Tender plaques | Dense neutrophils | Malignancy |
| Erosive pustular dermatosis | Elderly scalp | Neutrophils | Trauma |
| Acne necrotica | Necrotic scalp papules | Folliculitis | Chronic |
🔍 🧪 Histopathology‑Focused Table (High‑Yield for Exams & Clinic)
1. Neutrophilic pustular dermatoses
| Condition | Key Histopathology | Hallmark Clue |
|---|---|---|
| Acropustulosis of Hallopeau | Subcorneal/intraepidermal pustules packed with neutrophils; psoriasiform hyperplasia | Looks like pustular psoriasis of the digits |
| Subcorneal pustular dermatosis (Sneddon–Wilkinson) | Pure subcorneal pustules of neutrophils; minimal spongiosis | “Half‑half blister” clinically; IgA paraprotein association |
| Sweet’s syndrome | Dense dermal neutrophilic infiltrate; papillary dermal oedema; no vasculitis | “Pseudovesiculation” corresponds to papillary oedema |
| Reiter’s keratoderma blennorrhagicum | Psoriasiform epidermis; neutrophils in stratum corneum (Munro microabscess‑like) | Histology identical to pustular psoriasis |
| Erosive pustular dermatosis of scalp | Neutrophilic pustules, erosions, crust; mixed inflammation; scarring | Chronic trauma → sterile pustules + scarring alopecia |
| Pyoderma gangrenosum (pustular variant) | Neutrophilic dermatosis; ulceration; undermined edge; sterile | Neutrophils dominate; vasculitis may be secondary |
| Acne necrotica | Necrotizing lymphocytic folliculitis; follicular destruction; crust | Follicular necrosis with lymphocytes ± neutrophils |
2. Eosinophilic pustular disorders
| Condition | Key Histopathology | Hallmark Clue |
|---|---|---|
| Eosinophilic pustular folliculitis (Ofuji) | Folliculocentric eosinophils; spongiosis; eosinophilic microabscesses | Eosinophils cluster around follicles |
| Incontinentia pigmenti (Stage 1) | Eosinophilic spongiosis; intraepidermal vesicles with eosinophils | Vesiculopustular stage packed with eosinophils |
| Erythema toxicum neonatorum | Eosinophils in follicular units; eosinophilic pustules | Follicle‑based eosinophils in neonate |
| Infantile EPF (variant) | Same as EPF: follicular eosinophils | Infantile distribution but identical histology |
3. Nutritional / metabolic pustular dermatoses
| Condition | Key Histopathology | Hallmark Clue |
|---|---|---|
| Acrodermatitis enteropathica (zinc deficiency) | Pallor of upper epidermis; parakeratosis; spongiosis; necrosis; pustules | “Psoriasiform + necrolysis” pattern |
| Glucagonoma syndrome (Necrolytic migratory erythema) | Epidermal necrolysis; parakeratosis; pallor; superficial pustules | Same necrolytic pattern as zinc deficiency |
4. Neonatal benign pustuloses
| Condition | Key Histopathology | Hallmark Clue |
|---|---|---|
| Transient neonatal pustular melanosis | Subcorneal pustules with neutrophils; later pigment in basal layer | Neutrophils → collarette → hyperpigmentation |
| Erythema toxicum neonatorum | Eosinophils in follicular units; eosinophilic pustules | Eosinophils (vs TNPM neutrophils) |
5. Miscellaneous follicular pustular disorders
| Condition | Key Histopathology | Hallmark Clue |
|---|---|---|
| Tycoon/Tycosis scalp (folliculitis decalvans variant) | Neutrophilic folliculitis; follicular destruction; fibrosis | Neutrophils + scarring alopecia |
| Acne necrotica | Necrotizing lymphocytic folliculitis | Crusted necrotic papules on scalp |
Image‑Based OSCE Stems (Dermatology Registrar Level)
Stem 1 — Acropustulosis of Hallopeau
You are shown an image of a distal finger with erythematous plaques, sterile pustules, and progressive nail plate destruction. The pustules cluster around the nail folds and extend onto the pulp. Question: What is the most likely diagnosis?
Stem 2 — Subcorneal pustular dermatosis (Sneddon–Wilkinson)
The image shows flaccid pustules on the trunk arranged in annular and serpiginous patterns, some with collarettes of scale. The pustules appear superficial and recur in crops. Question: What condition is shown?
Stem 3 — Sweet’s syndrome
A photograph shows juicy, tender, erythematous plaques with pseudovesiculation on the upper limb. The patient appears systemically unwell. Question: What is the diagnosis?
Stem 4 — Reiter’s keratoderma blenorrhagicum
The image shows hyperkeratotic pustular plaques on the palms and soles, resembling pustular psoriasis. The patient has a history of urethritis and arthritis. Question: What is the likely cutaneous manifestation?
Stem 5 — Erosive pustular dermatosis of the scalp
An elderly patient presents with erosions, crusts, and sterile pustules on an atrophic scalp, with areas of scarring alopecia. Question: What is the diagnosis?
Stem 6 — Pyoderma gangrenosum (pustular variant)
The image shows a painful ulcer with a violaceous undermined border, surrounded by pustules. The patient has known IBD. Question: What is the most likely diagnosis?
Stem 7 — Acne necrotica
The photo shows small necrotic papules with central crusting on the scalp and hairline, some healing with pitted scars. Question: What is the diagnosis?
Stem 8 — Eosinophilic pustular folliculitis (Ofuji)
The image shows annular plaques with follicular pustules on the face and trunk. The lesions are intensely pruritic. Question: What condition is shown?
Stem 9 — Incontinentia pigmenti (Stage 1)
A neonate has linear vesiculopustular lesions along Blaschko’s lines on the limbs. Question: What is the diagnosis?
Stem 10 — Erythema toxicum neonatorum
A newborn (day 2 of life) has erythematous macules and papules with small pustules, sparing the palms and soles. Question: What benign neonatal condition is shown?
Stem 11 — Transient neonatal pustular melanosis
A newborn has fragile pustules that have ruptured to leave collarettes of scale and hyperpigmented macules. Present at birth. Question: What is the diagnosis?
Stem 12 — Acrodermatitis enteropathica
The image shows acral and periorificial dermatitis with pustules, erosions, and crusting, in a child with diarrhoea and alopecia. Question: What deficiency causes this condition?
Stem 13 — Glucagonoma syndrome (Necrolytic migratory erythema)
The photo shows erythematous plaques with superficial necrosis, crusting, and pustules, predominantly in intertriginous and acral areas. Question: What systemic condition is associated?
Stem 14 — Tycosis/Tycoon scalp (folliculitis decalvans variant)
The image shows tufted folliculitis, pustules around hair follicles, and progressive scarring alopecia. Question: What is the diagnosis?
