A case of herpetiform pemphigus with anti-desmoglein 3 IgG autoantibodies

Herpetiform pemphigus (HP) is a rare variant of pemphigus characterized by a unique clinical phenotype of erythematous or urticarial plaques and vesicles that present in a herpetiform arrangement. Most HP cases have circulating anti-desmoglein 1 (Dsg1) IgG autoantibodies, but some HP cases have anti-desmoglein 3 (Dsg3) IgG. A 92-year-old Japanese woman presented with severely pruritic annular erythema and vesicles in a herpetiform arrangement on the trunk. No oral mucosal lesions were present. Histopathologically, these vesicles showed eosinophilic spongiosis as well as suprabasilar acantholysis. Direct immunofluorescence showed in vivo IgG deposition on keratinocyte cell surfaces, and indirect immunofluorescence showed circulating IgG autoantibodies against keratinocyte cell surfaces at a titer of 1:30. Enzyme-linked immunosorbent assay using recombinant Dsg1 and Dsg3 revealed the presence of anti-Dsg3 IgG but no anti-Dsg1 IgG autoantibodies. The lack of oral mucosal involvement and the unique clinical features favored the diagnosis of HP. It remains to be clarified why the anti-Dsg3 IgG autoantibodies in this patient induced this unique features of HP, rather than the mucosal dominant type of pemphigus vulgaris.