Puzzles in practice. Diabetic dermopathy.

A 63-year-old white man is seen for a routine examination. His medical history is significant for type 2 diabetes mellitus of 16 years duration, diabetic peripheral sensory neuropathy, hypertension, and hyperlipidemia. He smoked 1 pack of cigarettes daily for 20 years but quit many years ago. Salient findings on physical examination include decreased light touch and vibratory sense in the feet, decreased pedal pulses, and hyperpigmented patches on the lower legs. The patches have normal sensation and a hint of atrophy. There is no overlying scale. What is your diagnosis?