Transverse melanonychia in a child receiving chemotherapy.

Transverse melanonychia is a rare finding often secondary to chemotherapy, orally ingested medications, or other iatrogenic interventions. A 19-month-old boy with hemophagocytic lymphohistiocytosis treated with biweekly etoposide and dexamethasone developed transverse bands of pigment in all toenail and fingernail units consistent with transverse melanonychia. We review the literature for reported cases of transverse melanonychia and summarize suspected etiologies.