For the 27 cases in which it has been reported, the mean age at onset of AN was about 4.5 years, with 2 patients affected at birth. Acanthosis nigricans was invariably present on the neck, and in 25 of 31 patients (81%), in the axillae (all 6 [100%] in the present study, and including involvement of the “flexors” described in 2 cases). Acanthosis nigricans was also found on the face (21 of 31 [68%]), chest (13 of 31 [42%]), abdomen (14 of 31 [45%]), groin (9 of 31 [29%]), upper extremities (7 of 31 [23%]), lower extremities (3 of 31 [10%]), and lower back (2 of 31 [6%]); the total number excludes cases in which location was not described. Acanthosis nigricans on the face was found around the eyelids, eyes, mouth, nose, and ears (Figure 1). On the abdomen, we found a predilection for the periumbilical area; on the extremities, in the antecubital and popliteal fossae. The neck and axillae were usually more severely affected (Figure 2). In most patients over time, the AN was severe, giving the skin an appearance resembling the bark of an oak tree.