Generalized bullous fixed drug eruption is distinct from Stevens-Johnson syndrome/toxic epidermal necrolysis by immunohistopathological features

Background Generalized bullous fixed drug eruption (GBFDE), a particular form of fixed drug eruption (FDE), is characterized by widespread blisters and erosions and can be confused with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Objective We sought to analyze specific features of GBFDE and differentiate it from SJS/TEN. Methods We retrospectively studied patients with GBFDE and SJS/TEN during a period of 10 years. GBFDE was defined as typical FDE lesions with blisters involving at least 10% body surface area on at least 3 of 6 different anatomic sites. Clinical presentations; histopathological features; immunohistochemical patterns of cluster-of- differentiation (CD)3, CD4, CD8, CD56, Fas, Fas ligand, granzyme B, perforin, granulysin, and forkhead box P3 (Foxp3); and serum granulysin levels were compared. Results Twenty-three cases of GBFDE were collected. Patients with GBFDE had shorter latent periods, less mucosal involvement, more eosinophil infiltration, and dermal melanophages. Lesional infiltrates in GBFDE had more dermal CD4⁺ cells including Foxp3⁺ regulatory T cells, fewer intraepidermal CD56⁺ cells, and fewer intraepidermal granulysin⁺ cells. The serum level of granulysin in GBFDE was also significantly lower than in SJS/TEN. Limitations The number of cases in this study is small. Conclusion GBFDE is a distinct disease distinguishable from SJS/TEN by particular features such as granulysin, CD56, and Foxp3 expressions.