Table I.

Classification of acanthosis nigricans as described by Sinha and Schwartz³

Type of acanthosis nigricans3	Features and findings2,3
Obesity associated	•Most common in children and adults •Insulin and insulin-like growth factor (IGF) are the stimulants for the proliferation of epidermal keratinocytes and dermal fibroblasts
Syndromic	•Type A insulin resistance syndrome (HAIR-AN syndrome), type B insulin resistance syndrome, Crouzon’s syndrome, gigantism, acromegaly, and Prader-Willi syndrome
Medication induced	•Most associated with nicotinic acid. •Other implicated medications include oral contraceptives, corticosteroids, methyl-testosterone, heroin, fusidic acid, hydantoin-like derivatives, and diethylstilbestol
Malignant	•Cutaneous manifestation of an underlying malignancy •Rare in pediatric population •Gastric adenocarcinoma is the most common
Acral	•Affects the knuckles, elbows, and knees
Unilateral	•Epidermal nevoid condition •May eventually become bilateral
Benign	•Rare, may be inherited in an autosomal dominant fashion with variable penetrance •Can either be congenital or develop in childhood or during adolescence •Palms of the hands and soles of the feet are usually spared •No underlying malignancy or metabolic derangement
Mixed type	•Consists of multiple subtypes