Detection of preleukemic state of adult T-cell leukemia (pre-ATL) in HTLV-1 carriers.

The prevalence of the preleukemic state of adult T-cell leukemia (pre-ATL) was studied in Nagasaki prefecture, one of the endemic human T-lymphotropic virus type 1 (HTLV-1) areas in Japan. Pre-ATL cases have the monoclonal proliferation of abnormal lymphocytes, without signs of malignant proliferation or clinical signs and symptoms related to leukemia. HTLV-1 carriers who have monoclonal integration of HTLV-1 proviral DNA may be at high risk of developing ATL. Abnormal lymphocytes with either bilobular or large and chromatin-rich nuclei were found in 63/356 (17.7%) of HTLV-1 carriers among inhabitants. We analyzed DNA of peripheral lymphocytes from 108 carries with abnormal lymphocytes by Southern blot technique. Monoclonal integration of HTLV-1 has been detected in 12 cases (11.1%). These results lead to the conclusion that the prevalence rate of pre-ATL among all HTLV-1 carriers is about 2%. Pre-ATL is presumed to be the clinical stage which precedes ATL, although the possibility remains that the HTLV-1 carrier may develop symptoms of ATL directly, without going through the pre-ATL stage.