MECHANISMS OF THROMBOCYTOPENIA INDUCED BY INTERFERON THERAPY FOR CHRONIC HEPATITIS-B

To clarify the mechanisms of thrombocytopenia observed in patients wit h chronic hepatitis B treated with interferon. We studied six patients with chronic active hepatitis B who received intramuscular injections of natural interferon-alpha (3 or 5 million IU/day) for 4 weeks. Peri pheral blood platelet counts, bone marrow findings, and platelet kinet ics, determined using In-111-labeled platelets, were analyzed. Platele ts decreased significantly 1 week after the beginning of treatment and remained decreased until the completion of treatment. The number of n ucleated cells and megakaryocytes in bone marrow decreased in three of five patients studied during treatment. The kinetic study showed plat elet survival time to be 8.1 +/- 1.3 days (range, 5.8-10.0). One day a fter platelet injection, platelets accumulated predominantly in the sp lenic area in all patients, whereas hepatic accumulation was predomina nt 7 days after injection in three of the six patients. Thrombocytopen ia during interferon treatment arises from the inhibition of stem cell proliferation and differentiation in the bone marrow and from the cap ture of platelets by the liver.