Abstract

Columnar dyskeratosis (also known as “pseudocornoid lamella”) is a rare histopathologic pattern describing intermittent foci of epidermal dells with vertical columns of dyskeratotic cells with mixed parakeratotic cells and underlying hypogranulosis. The true cornoid lamella as described in porokeratosis exhibits a column of compact parakeratosis oriented at a 45 degree angle with underlying dyskeratotic cells and reduced granular layer. Columnar dyskeratosis is associated with Wong-type dermatomyositis, but this can also be a helpful histopathologic clue in the diagnosis of classic dermatomyositis. Herein, we present a case of a 69-year-old woman with history of myelofibrosis and acute myeloid leukemia who presented with a two-week history of a rash consisting of violaceous papules coalescing into plaques on the face, trunk, and upper and lower extremities. She reported a history of chronic hydroxyurea exposure, which was discontinued two months prior to the rash onset. Two punch biopsies were performed which revealed columnar dyskeratosis, along with a cell-poor interface dermatitis, colloid bodies, and sparse dermal inflammation. Based on clinicopathologic correlation, the patient was diagnosed with hydroxyurea-induced amyopathic dermatomyositis. This case highlights the helpful clue of columnar dyskeratosis in the diagnosis of dermatomyositis given the narrow differential diagnosis for this uncommon histopathologic feature.