Treatment of thrombocytosis in chronic myeloproliferative disorders with interferon alfa-2b.

Thirty-six patients with chronic myeloproliferative disorders (CMPD) with thrombocytosis (essential thrombocythaemia 19 patients, chronic megakaryocytic granulocytic myelosis five, polycythaemia vera six, chronic myelogenous leukaemia six) were treated with interferon alfa-2b to reduce the platelet count. The pre-treatment platelet count was in the range 450-700 x 10(9)/L in eight patients, 700-1000 x 10(9)/L in eight and above 1000 x 10(9)/L in 20. In the induction phase of treatment 22 patients were treated with interferon alfa-2b 3 million units (MU) daily subcutaneously for 2 months or until the platelet count returned to normal, if earlier.