Adult T-cell leukemia/lymphoma is a T-cell malignancy caused by the human T-cell lymphotropic virus-I. Adult T-cell leukemia/lymphoma is primarily a disease of adults due to the long latency period between initial infection and development of leukemia. We present a case of acute adult T-cell leukemia/lymphoma in an adolescent. Skin lesions had appeared 3 years earlier and were the initial sign of human T-cell lymphotropic virus-I infection and T-cell malignancy. Her disease failed to respond to both intensive chemotherapy and antiviral therapy. Cutaneous lesions are sometimes the initial sign of adult T-cell leukemia/lymphoma and early recognition is imperative. © 2008 The Authors.