Extensive bullous eruption with pauci-inflammatory subepidermal blister: Direct immunofluorescence (DIF) makes the DIFference

Summary: Bullous systemic lupus erythematosus (BSLE) is a rare acute vesiculobullous eruption most commonly on the trunk and extensor surfaces. Most patients have an underlying history of systemic lupus erythematous; however, the cutaneous bullous eruption can infrequently be the first presentation. A 70-year-old male without a prior history of autoimmune disease presented with a three-month history of an extensive cutaneous eruption involving the genitals and oral mucosa and 30-pound weight loss. Physical examination revealed large, eroded patches on the trunk, extremities, and genitals with tense bullae noted on the right thenar eminence and left lateral tongue. A shave biopsy showed a cell-poor subepidermal blister with no interface changes and minimal inflammation. Direct immunofluorescence revealed full-house granular/pseudo-linear deposition of immunoglobulins along the basement membrane zone and superficial dermis. Our patient’s case is unique in several ways, given his age at diagnosis, lack of prior history of systemic lupus erythematous, and pauci-inflammatory histopathology. While the differential for full-body bullous eruptions is broad, direct immunofluorescence was critical in making the diagnosis and ensuring further work-up and appropriate treatment for this patient.