Confluent and reticulated papillomatosis is a dermatologic disorder characterized by onset in the teenage or young adult years of hyperkeratotic 1- to 2-mm papules that increase in size to 4 to 5 mm and coalesce to form a reticular pattern peripherally and a confluent pattern centrally. Early papules can be erythematous and later turn brown. Affected individuals are usually otherwise asymptomatic. The condition is distinct from acanthosis nigricans and tinea versicolor (infection with the yeast Pityrosporum), but can appear similar. Microscopic examination of skin biopsy shows epidermal undulation with hyperkeratosis, squat papillomatosis, and occasional acanthotic downward projections from the bases of the dells between papillomatous areas. Antibacterial agents such as minocycline and azithromycin are effective, perhaps due to their antiinflammatory and immunomodulatory properties (summary by Scheinfeld, 2006). [from
OMIM]