Dermatosis papulosa nigra: a clinically and histopathologically distinct entity

Dermatosis papulosa nigra was first described by Aldo Castellani (1874-1971) more than 90 years ago, and it has since been presumed to be a variant of seborrheic keratosis. Despite their morphologic similarities both macroscopically and microscopically, key differences have yet to be explained. These lesions also exhibit different demographics, with dermatosis papulosa nigra having a predilection for dark-skinned individuals and a female predominance. No studies to date have investigated this, but studies assessing the mechanisms of similar dermatologic conditions may yield significant clues. The additional impact of environmental factors may also be important, but much controversy exists. Further investigations into dermatosis papulosa nigra are necessary to determine its pathogenesis and whether it should be regarded as a distinct entity.