Case of shift from linear immunoglobulin A bullous dermatosis to pemphigus herpetiformis for a short period of time.

Pemphigus herpetiformis (PH) is a rare variant of pemphigus characterized by erythemas and vesicles, tending to present with annular-shaped lesions. Immunologically, immunoglobulin (Ig)G deposition at the keratinocyte cell surfaces is observed. Linear IgA bullous dermatosis (LABD) is a rare subepidermal blistering disease with linear IgA deposits at the epidermal basement membrane zone (BMZ). The annular-shaped skin lesions in PH mimic clinical manifestation of other autoimmune bullous diseases, including LABD, although PH and LABD have different immunological and histopathological features. Herein, we report the first case of a shift from LABD to PH. A 70-year-old Japanese man presented annular erythemas surrounded by vesicles on the trunk and extremities. Histopathological examination revealed subepidermal bullae and eosinophilic spongiosis. Direct immunofluorescence demonstrated linear IgA deposits at the epidermal BMZ. Immunoblot analyses of normal human epidermal and dermal extracts, supernatant of HaCaT cells, recombinant proteins of BP180 NC16a and C-terminal domains, and purified laminin-332 showed no reactivity for either IgG or IgA. IgG chemiluminescent enzyme immunoassays for desmogleins 1 and 3, and BP180 were all negative. These findings led to the diagnosis of sole LABD. Although oral prednisolone temporarily improved the skin lesions, annular erythema without vesicles remained. A new skin biopsy revealed subcorneal pustules with eosinophils, but no subepidermal bullae. Direct immunofluorescence revealed IgG and C3 deposition at the keratinocyte cell surfaces. IgG enzyme-linked immunosorbent assay for mammalian desmocollins 1-3 revealed desmocollin 1 reactivity. Based on these findings, we made a diagnosis of sole PH.