A Case of Adult T-cell Leukemia/Lymphoma with an Indolent Clinical Course has an Unusual Proviral DNA Integration Pattern

Sir, Adult T-cell leukemia/lymphoma (ATL) is a peripheral T-cell malignancy caused by human T-cell lymphotrophic virus type I (HTLV-I). The characteristic clinical features of ATL include generalized lymphadenopathy, leukemic cells of T-cell origin with highly convoluted nuclei, skin involvement, hypercalcemia and rapid progress of the clinical course. Relatively high rates of HTLV-I infection are observed in parts of Japan, the Caribbean, South America and Africa (1). The transmission of HTLV-I is mainly from mother to child through breast-feeding (2). The subsequent integration of the HTLV-I provirus into T cells is thought to be a random event that occurs during the carrier state. Polyclonal integration patterns of HTLV-I proviral DNA have been demonstrated by Southern blot analysis as the so-called smear pattern in asymptomatic HTLV-I carriers. Of these randomly infected cells, a cell clone is thought to be selected for preferential growth. Although the mechanism of clonal selection remains unclear, the HTLV-I proviral DNA integration pattern can progress from undetectable to polyclonal, or to monoclonal (1). Recently, we encountered a patient with ATL with an indolent clinical course.