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Inflammatory dermatopathology — reaction patterns, blisters and immunofluorescence
Inflammatory skin diseases are read on biopsy by reaction pattern — spongiotic, psoriasiform, interface, vesiculobullous and granulomatous — and in blistering diseases the level of the split and the direct immunofluorescence pattern decide the diagnosis.
Why it matters in the exam
The bank asks about pemphigus, pemphigoid and recognisable patterns. In the spongiotic pattern there is oedema between epidermal cells — eczema and contact dermatitis. In psoriasis there is regular thickening of the epidermis, parakeratosis with neutrophils (Munro microabscesses), loss of the granular layer and dilated capillaries in the papillae. In lichen planus there is a band-like lymphocytic infiltrate along the junction, a thickened granular layer, "saw-tooth" rete ridges and dead keratinocytes (Civatte bodies). In cutaneous lupus there is vacuolar damage of the basal layer, basement-membrane thickening, perivascular and periadnexal infiltrate and mucin.
In blistering diseases: pemphigus vulgaris — a split above the basal layer with acantholysis, basal cells remaining like a "row of tombstones", antibodies against desmoglein 3 (and with skin involvement also desmoglein 1), and on immunofluorescence intercellular IgG in a "net" pattern. Involvement of the oral mucosa together with scalp, face and axilla fits pemphigus vulgaris. Bullous pemphigoid — a split below the epidermis with eosinophils in older adults, and linear IgG and C3 along the basement membrane. Dermatitis herpetiformis — neutrophils at the tips of the papillae, granular IgA in the papillae, and an association with coeliac disease.
Granulomas in the skin: sarcoidosis with "naked" granulomas, and palisading granulomas — granuloma annulare with central mucin, and the subcutaneous rheumatoid nodule with central fibrinoid necrosis and cells arranged around it, in a patient with rheumatoid arthritis. Leukocytoclastic cutaneous vasculitis shows fragmenting neutrophils and fibrinoid necrosis in venules. A working rule: a biopsy for immunofluorescence is taken from normal skin next to the blister and sent in a suitable medium, not in formalin.
Key points
- Patterns: spongiotic, psoriasiform, interface, vesiculobullous, granulomatous.
- Pemphigus vulgaris: above the basal layer, desmoglein 3, IgG in a net.
- Pemphigoid: below the epidermis, eosinophils, linear IgG and C3.
- Dermatitis herpetiformis: IgA in the papillae and coeliac disease.
- Rheumatoid nodule: palisading granuloma with fibrinoid necrosis.
Summary table
| Pattern or disease | Level or feature | Immunofluorescence | Clinical example |
|---|---|---|---|
| Spongiotic | Oedema between keratinocytes | — | Eczema, contact dermatitis |
| Psoriasiform | Regular thickening, parakeratosis with neutrophils | — | Psoriasis |
| Interface | Basal-layer damage, band infiltrate | In lupus: deposit at basement membrane | Lichen planus, lupus |
| Pemphigus vulgaris | Split above the basal layer, acantholysis | Intercellular IgG in a net | Oral mucosa, scalp |
| Bullous pemphigoid | Split below the epidermis, eosinophils | Linear IgG and C3 at basement membrane | Older adults, itch |
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Sources
- Weedon's Skin Pathology, 5th edition (2020) — The major tissue reaction patterns
- Lever's Histopathology of the Skin, 12th edition (2023) — Vesiculobullous diseases and immunofluorescence
- Robbins and Cotran Pathologic Basis of Disease, 10th edition (2021) — The skin — inflammatory and blistering disorders
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.