Transverse melanonychia is a rarely reported phenomenon that is characterized by transverse brown or gray pigmentation of the nails. It is often drug-induced. Chemotherapeutic agents (including dasatinib, imatinib, cyclophosphamide, adriamycin, hydroxyurea, bleomycin, and etoposide) have been noted to induce transverse melanonychia. Other case reports have detailed electron beam therapy, quinacrine, infliximab, and zidovudine as inciting causes. Melanocyte activation is thought to be responsible pathomechanistically.