A case with adult T-cell leukemia was reported. A 52-year-old man had suffered from low back, bilateral hip joint, and bilateral thigh pain for three years. Multiple osteolytic lesions were found on roentgenogram. Laboratory examination showed normal serum calcium, low serum phosphorus, high serum alkalinephosphatase activity, and normal parathyroid hormone level. Anti HTLV-1 antibody dwas positive and flower cells were found in peripheral blood. Bone biopsy was performed in right femur. Proliferation of osteoclasts and excessive bone resorption were observed but not ATL cells.
