A 70-year-old woman with well-controlled Type 2 diabetes and multiple myeloma in complete remission presented for peripheral blood hematopoietic progenitor cells collection. She had completed five 28-day cycles of standard 4-drug induction therapy, including lenalidomide 25mg daily, 21 days/cycle, with the last dose of lenalidomide 3 weeks prior. She reported a 2-week history of darkened palms and soles. Physical exam revealed asymmetric, poorly demarcated, dark-brown macules-to-patches broadly distributed over bilateral palms and soles. The hyperpigmented areas were not erythematous, painful, or solely intertriginous. Bilateral soles were mildly pruritic. Hemoglobin was 13.1 grams per deciliter (reference range, 12.0-16.0) without transfusion.

Immunomodulatory drug-associated hyperpigmentation, disproportionately affecting Black patients and commonly occurring within months of therapy initiation, was diagnosed. Informed consent should include discussion of this entity, which is often not wholly reversible and is potentially distressing to patients. At follow-up 7 weeks later, the hyperpigmentation was unchanged.