Benign Acanthosis Nigricans

Hyperpigmentation involving the neck developed in this 8-year-old obese girl. The affected area resembled unwashed skin. The patient had worn a uniform to school-a jumper and blouse with a collar-for 6 months.

All laboratory findings, including complete blood chemistries, adrenal and thyroid hormone levels, and melanin and iron assessments, were within normal limits. Her young age and lack of symptoms precluded consideration of a malignancy. Benign acanthosis nigricans, or pseudoacanthosis nigricans, was diagnosed.

The majority of benign acanthosis nigricans cases are associated with heat and friction in flexural folds. Indeed, after school ended for the year and this girl no longer wore her collared blouse, the hyperpigmentation spontaneously cleared. Reassurance was the only treatment necessary.