Pemphigus Foliaceus

Pemphigus foliaceus (PF) is a superficial autoimmune acantholytic blistering disease with antibodies against desmoglein 1, producing subcorneal blisters without significant mucosal disease.

• Endemic variant (fogo selvagem) occurs in rural Brazil and parts of Latin America, linked to black fly (Simulium) bites; sporadic variant is worldwide, seen at 40 to 60 years.
• Drug induced PF: penicillamine, captopril, enalapril, rifampicin, cephalosporins, and phenylbutazone.
• Carries a better prognosis than pemphigus vulgaris, with chronic relapsing course.

• Scaly, crusted, erythematous erosions in seborrhoeic areas (scalp, face, upper trunk), often with only fleeting flaccid blisters since the roof is thin.
• Burning or pain, rarely itch. Nikolsky sign positive.
• Mucosal surfaces spared. Erythrodermic form can occur.
• Overlap with seborrhoeic dermatitis, impetigo and lupus erythematosus (pemphigus erythematosus).

• Biopsy: subcorneal or granular layer acantholysis.
• DIF: intercellular IgG, C3 in upper epidermis (or the full thickness).
• ELISA for anti-Dsg1 positive and anti-Dsg3 negative.
• Exclude bullous impetigo, staphylococcal scalded skin syndrome, subcorneal pustular dermatosis, pemphigus vulgaris, and drug causes.
• Baseline before therapy: HbA1c, lipids, bone density, hepatitis B and C, HIV, TB screen and TPMT.

• Localised disease: clobetasol 0.05% ointment twice daily, tacrolimus 0.1% for facial areas, with or without intralesional triamcinolone 5 to 10 mg/mL.
• Moderate disease: prednisolone 0.5 to 1 mg/kg/day, with dapsone 50 to 150 mg daily (check G6PD), or azathioprine 2 to 3 mg/kg, or mycophenolate 1 to 1.5 g twice daily.
• Severe or refractory: rituximab 1000 mg on days 1 and 15 (or 375 mg/m2 weekly for 4 weeks), IVIG, plasmapheresis.
• Stop implicated drugs; drug induced forms often resolve.
• Sun avoidance (UV can flare), topical antiseptics for crusts, and Pneumocystis and bone prophylaxis on prolonged steroids.
• Taper steroids slowly; monitor anti-Dsg1 titres.