Flame figures in linear IgA bullous dermatosis: a novel histopathologic finding.

BACKGROUND: Linear IgA bullous dermatosis (LABD) is an autoimmune subepidermal blistering disease usually with a neutrophil rich inflammatory infiltrate, and characterized by linear IgA deposition at the basement membrane zone (BMZ), and neutrophil predominant dermal inflammation. We report a case of LABD with numerous eosinophils and flame figure formation, a unique histopathologic finding not previously reported. A 69-year-old woman presented with a rapidly progressive, intensely pruritic rash over forearms, breasts, axillae, hips, and thighs. Thelesions were comprised of annular vesicles and bullae with hemorrhagic crusts and erosions. The clinical differential diagnosis included bullous pemphigoid(BP), LABD, and epidermolysis bullosa aquisita (EBA).

RESULTS: A biopsy from a bullous plaque on the wrist revealed a subepidermal blister with neutrophils and numerous eosinophils with flame figure formation.Direct immunofluorescent (DIF) microscopy revealed linear deposition of IgA at the BMZ.

CONCLUSIONS: Although unusual, the combined findings supported a diagnosis of LABD. Increased eosinophils may be associated with drug-induced LABD and may explain the numerous eosinophils in our case. It is important to be aware of this finding as the pathology may easily be misdiagnosed as BP, or possibly bullousWells syndrome. This case emphasizes that combined clinical, pathologic, and DIF findings are essential in the diagnosis of bullous dermatoses.