Adult T-cell leukemia.

Adult T-cell leukemia (ATL) is endemic in southwestern Japan, in the Caribbean islands, and in central Africa. Human T-cell lymphotropic virus type I (HTLV-I) is the etiologic agent of ATL. The clinical characteristics are (1) onset in adulthood, (2) subacute or chronic leukemia with rapidly progressive terminal course, (3) frequent skin lesions, (4) lymphadenopathy that characteristically spares the mediastinum, (5) hepatosplenomegaly, (6) hypercalcemia, and (7) a tendency toward geographical clustering. Although hypercalcemia and osteoclastic activity due to parathyroid hormone-related peptide are frequently reported histologically, radiographic abnormalities of bone are not common. Two major patterns of osteolytic lesions observed in ATL are "punched-out" lesions resembling multiple myeloma and osteolytic metastasis and subperiosteal bone resorptions similar to those in hyperparathyroidism.