Background: Adult T-cell leukemia-lymphoma (ATL) can occur in siblings infected with HTLV-1.
Case reports: Two Caribbean siblings developed ATL a few years apart. One case has been reported previously. Both individuals had peripheral lymph node T-cell lymphoma and a few atypical lymphocytes on blood smear. Lymphocytosis, bone marrow biopsy, abdominal computed tomographic scanning, and chest radiography were normal. Clonal rearrangement of T-cell receptor was present in skin lesions for both patients and in the blood for one. HTLV-1 serology was positive. Clonal integration of HTLV-1 provirus was demonstrated in skin lesions in one patient and in blood lymphocytes in the other. Chemotherapy, then interferon alpha, were unsuccessful in the first patient. Topical metchloretamine was partially effective for the second patient.
Discussion: ATL in siblings is explained by mother-to-child transmission of HTLV-1 infection during breastfeeding.