A 71-year-old man presented with progressive black discoloration on the dorsal surfaces of both feet that had been present for 2 years. The discoloration was not associated with pain, burning, or itching. In the previous 6 months, the discoloration had advanced to his distal legs and then separately developed in the preauricular area.

The patient had a history of coronary artery disease, type 2 diabetes, and chronic nodulocystic acne. He was a nonsmoker with no known drug allergies. He had no family history of similar skin findings.

Physical examination confirmed a bluish papular discoloration on both feet as well as his face and ears (Figure 1 and Figure 2). These areas were not tender.

QUESTION

Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?

• A. Acanthosis nigricans.

• B. Addison disease.

• C. Chronic venous stasis.

• D. Drug-induced pigmentation.

• E. Melasma.

DISCUSSION

The correct answer is D: drug-induced pigmentation due to long-term minocycline use for treatment of chronic nodulocystic acne. The hyperpigmentation started on the dorsal aspect of the feet with a classic blue and black discoloration. With continued minocycline use, areas of pigmentation darkened and spread proximally.