A Rapidly Progressive Bullous Eruption in a Toddler.

Linear IgA bullous dermatosis (LABD) is a rare autoimmune blistering disorder characterized by subepidermal vesiculobullous eruptions and a variable clinical presentation. In pediatric patients, LABD may present as rapidly progressive and widespread disease, often mimicking other severe blistering conditions and complicating early diagnosis. We report a case of a toddler with a two-week history of a progressive bullous eruption involving the extremities, lower abdomen, perioral region, and genitals, with sparing of the oral mucosa. Examination revealed a combination of flaccid hemorrhagic bullae and tense vesicles, with a negative Nikolsky sign. The extent and morphology of the eruption prompted evaluation for multiple serious blistering disorders. Histopathologic examination with direct immunofluorescence demonstrated linear IgA deposition along the basement membrane zone, confirming the diagnosis of LABD. The patient was treated with systemic corticosteroids followed by dapsone, resulting in marked clinical improvement and near-complete resolution. This case emphasizes the importance of recognizing atypical and rapidly evolving presentations of LABD and highlights the role of early biopsy and timely immunomodulatory therapy in achieving favorable outcomes.