Linear IgA Bullous Dermatosis

Linear IgA bullous dermatosis (LABD) is a subepidermal blistering disease characterised by linear deposition of IgA along the basement membrane zone. In children, it is termed chronic bullous disease of childhood.

• Rare (0.5 per million per year). Bimodal onset: preschool children and adults over 60.
• Target antigens: a 97 kDa fragment of BP180 (LAD-1/LABD97) and type VII collagen.
• Drug induced LABD: vancomycin (commonest), also penicillins, cephalosporins, trimethoprim-sulfamethoxazole, captopril, phenytoin, lithium, NSAIDs, and amiodarone.
• Associated with ulcerative colitis, lymphoma and other malignancies in adults.

• Tense vesicles and bullae in an annular or rosette arrangement ("string of pearls" or "crown of jewels") on erythematous skin.
• Children: perineal, perioral, and lower trunk involvement. Adults: trunk, extensors, face, and scalp.
• Itch and burning; mucosal lesions (oral, ocular) in some, with a risk of conjunctival scarring.
• Drug induced forms can be mimicked by toxic epidermal necrolysis.

• Biopsy: subepidermal blister with neutrophils at the tips of papillae.
• DIF: linear IgA (with or without C3) along the basement membrane zone, confirming diagnosis. Salt split skin: IgA deposits on the epidermal side (roof), less commonly dermal.
• Exclude dermatitis herpetiformis (granular IgA), bullous pemphigoid, mucous membrane pemphigoid, epidermolysis bullosa acquisita, and impetigo.
• Medication history for new drugs in the preceding weeks.
• In adults, screen for malignancy and inflammatory bowel disease.

• Stop causative drugs; drug induced LABD usually clears within weeks.
• Dapsone 0.5 to 2 mg/kg/day in children (25 to 50 mg start) or 50 to 150 mg in adults, after checking G6PD, with full blood count and methaemoglobin monitoring. Response is rapid.
• Sulfapyridine 1 to 1.5 g/day or sulfasalazine 1 to 4 g/day for dapsone intolerance.
• Prednisolone 0.5 to 1 mg/kg/day (short course) for severe disease or while dapsone takes effect.
• Refractory: colchicine 0.5 to 1.5 mg/day, mycophenolate, methotrexate, rituximab, IVIG.
• Topical clobetasol for localised lesions, ophthalmology review for ocular disease, and wound care.
• Children usually remit within 2 to 4 years, with treatment tapered. Adults often need longer therapy.