Dear Editor, Nevoid acanthosis nigricans (AN) is a rare form of AN that can manifest with a characteristic nevoid appearance and has histological features similar to other forms of AN.1 It is not associated with any known syndrome, endocrinopathy, drugs or internal malignancy. Two cases of nevoid AN involving the umbilicus have been reported. We present another case of nevoid AN localized to the umbilicus and briefly review the pertinent published work.A 16-year-old female presented with an asymptomatic, dark-brownish plaque on the umbilicus. At the age of 12, a small pigmented patch appeared on her umbilicus, and slowly increased in size over a 4-year period. She was not obese and had a normal menstrual cycle. She had not taken any medication over the past 4 years, and her family history was unremarkable. Physical examination demonstrated a hyperpigmented, velvety plaque on the umbilicus (Fig. 1). No other cutaneous or mucosal lesions were observed. Routine laboratory evaluations, including a complete blood count, serum chemistry, urine analysis and plasma glucose level showed no abnormalities. A thyroid function test was within normal limits. Histopathological examination of the lesion showed hyperkeratosis, acanthosis, papillomatosis and a mild perivascular lymphocytic infiltration in the superficial dermis (Fig. 2). Treatment with minocycline and topical 0.1% adapalene was started. The patient was not compliant with the therapy and no significant improvement was noticed on follow up at 7 weeks.Acanthosis nigricans commonly presents as graybrown, velvety plaques in any location, but predominantly in the intertriginous areas such as the axillae, the neck, and the genital and submammary regions. 2 AN is best classified based on the underlying problems or causes: insulin resistance-related, malignancyrelated, drug-induced, idiopathic and others, which include syndromic, acral and nevoid.1,2 The histology of AN is consistent regardless of clinical associations.The characteristic features include hyperkeratosis and papillomatosis but only slight, irregular acanthosis and usually no hyperpigmentation.3 Nevoid AN is a rare benign form of AN with a localized distribution, manifesting at birth, childhood or puberty. It tends to enlarge for a time and then remains stable or regresses. Nevoid AN has been reported as a unilateral presentation, which