BCR rearrangement in apparent essential thrombocythaemia.

The presence of the Philadelphia chromosome is a major determinant of the prognosis of patients with myeloproliferative disorders. We describe a case of apparent essential thrombocythaemia in whom cytogenetic analysis was normal. However, the presence of basophilia, the absence of abnormal megakaryocytes in a trephine biopsy and the female sex of the patient prompted Southern analysis of peripheral granulocyte DNA. This revealed a BCR rearrangement and the patient has therefore undergone allogeneic bone marrow transplantation. This case emphasizes the importance of both cytogenetic and molecular analysis of patients with apparent essential thrombocythaemia.