What Is Your Diagnosis? Mees Lines and Beau Lines

A 38-year-old man presented to the dermatology clinic with multiple parallel transverse white bands and several painless transverse depressions involving all 10 fingernails. The banding did not dissipate with pressure and the pressure did not elicit pain or tenderness. The patient denied any associated symptoms and reported no history of nail trauma. At the time of presentation, the patient was undergoing a remission-induction regimen for acute promyelocytic leukemia that included all-trans-retinoic acid in conjunction with arsenic trioxide.