Diagnosing Pemphigus Foliaceus: A Rare Blistering Disease Masquerading as a Common Dermatologic Disorder.

Pemphigus foliaceus (PF) is an autoimmune dermatologic disease that typically presents with painful, superficial blisters that evolve into scaling erosions in a seborrheic distribution. This case study intends to demonstrate that due to the relative scarcity of the disease and its distribution on the body, PF can easily be misdiagnosed. We present a 43-year-old African American male that presented to the dermatology clinic with an 18-month history of non-pruritic, violaceous, scaling patches and plaques most prominent on the malar cheeks, upper chest and upper back. He had been evaluated at an outside hospital with a high suspicion for cutaneous lupus erythematosus (CLE) and seborrheic dermatitis. However, repeated biopsies revealed non-specific spongiotic dermatitis, not consistent with CLE or seborrheic dermatitis. Over the subsequent months, he received treatment for both conditions without improvement in his symptoms. When he was referred to our dermatology clinic, repeat biopsies were obtained which demonstrated acantholysis and dyskeratosis in the granular layer, consistent with PF. Direct immunofluorescence revealed intercellular IgG staining most prominent in the epidermis, also consistent with PF. Finally, enzyme-linked immunosorbent assay for anti-desmoglein 1 returned positive, confirming the diagnosis. Upon review of the previous biopsies, focal areas of acantholysis and dyskeratosis were noted in the granular layer, which would have pointed away from a diagnosis of CLE or seborrheic dermatitis if PF was included in the clinical differential diagnosis. This case serves as a reminder that when there is a discrepancy in clinical-pathologic correlation, it is important to revisit the case and consider other pathologies.