Development of pemphigus herpetiformis in a patient with psoriasis receiving UV-light treatment.

BACKGROUND: Pemphigus is an autoimmune blistering disease of the skin and mucous membranes. Pemphigus herpetiformis, a rare variant of pemphigus, is characterized by erythematous, vesicular, bullous, or papular lesions in a herpetiform pattern, often associated with pruritus. Clinical cases documenting the development of pemphigus in patients with a history of psoriasis have been reported in the literature.
METHODS: We used immunological methods to study a case in which pemphigus herpetiformis occurred in a woman with a history of psoriasis, shortly after a course of ultraviolet B (UVB) therapy.
RESULTS: Histopathology revealed a subcorneal blister with prominent neutrophilic infiltration. Immunopathology detected in situ bound and circulating immunoglobulin G (IgG) autoantibodies to epithelial cell surfaces and circulating IgG autoantibodies against desmoglein 1. The patient was also found to have Hashimoto's thyroiditis.
CONCLUSIONS: This case illuminates a possible role of UV therapy in the induction of pemphigus herpetiformis through an epitope-spreading mechanism. The patient's autoimmune thyroiditis may also contribute to the predisposition for pemphigus development. The histopathological findings in pemphigus patients with a history of psoriasis may resemble Munro's microabscesses of psoriasis and should therefore alert pathologists and clinicians in considering additional diagnostic methods such as direct and indirect immunofluorescence.