Background: Types of subepidermal autoimmune bullous dermatosis (AIBD) are classified by anatomoclinical picture and target antigen. A new entity has recently been identified: anti-p200 pemphigoid.
Patients and methods: An 82-year-old man consulted for a profuse pruritic bullous eruption refractory to the standard treatments for bullous pemphigoid (BP). Direct immunofluorescence examination of a skin biopsy revealed linear deposits of IgG and of C3 at the dermal-epidermal junction, but Elisa screening for circulating anti-BP180 and anti-BP230 antibodies was negative. Indirect immunofluorescence (IIF) testing of cleaved skin revealed a deposit of IgG4 antibodies on the dermal side. Immunoblotting was negative for a dermal extract but showed an antibody directed against a 200-kD epidermal antigen. A diagnosis of anti-p200 pemphigoid was eventually made and the patient was successfully treated with dapsone.
Discussion: The diagnosis of anti-p200 pemphigoid was made in this case in spite of discrepancy between the IIF and immunoblotting results, and despite the fact that the target antigen in this disease is considered as being restricted to dermal sites. Anti-p200 pemphigoid usually begins in the second part of life and differs from standard bullous pemphigoid in terms of more frequent mucous membrane and cephalic involvement, as well as a greater degree of miliary scarring. This disease appears more prominent in males and is associated with psoriasis in around one third of cases. Autoantibodies recognize laminin gamma-1, an extra-desmosomal protein that contributes to dermal-epidermal adhesion.
Conclusion: This recently described disease as probably under-diagnosed in France. It should be considered in atypical presentations of bullous disease. Diagnosis is confirmed by immunoblotting detection of autoantibodies directed against a 200-kD antigen normally present in the extract. Dapsone appears to be the most effective treatment.
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