This obese 18-year-old has had a brown, scaly rash for 4 years. The rash spread from his neck, where it initially developed, to his chest and back. It is asymptomatic but of significant concern. His obesity has been an issue since early childhood. A skin biopsy specimen showed papillomatosis, acanthosis, and increased melanin. The rash’s morphological similarity to acanthosis nigricans and the history of obesity suggest confluent and reticulated papillomatosis.
From researchers’ attempts to define the cause of confluent and reticulated papillomatosis, the following basic themes have emerged:
• Endocrine—the association with obesity and puberty and the morphological similarity of the rash to acanthosis nigricans suggests diabetes as the cause.
• Musculoskeletal—the nature of the primary papules suggests a disturbance of keratinization.
• Infectious—the location and morphology of the rash suggest an exaggerated response to Pityrosporum ovale, the infectious organism responsible for tinea versicolor.