Primary Myelofibrosis with Myeloid Metaplasia and Cytogenetically Abnormal Clones in 2 Children with Down's Syndrome

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Abstract
Two children with Down''s syndrome showed severe anemia, leukocytosis with blastic cells, thrombocytopenia and hepatosplenomegaly. Bone marrow aspirations were near-dry tap and marrow biopsy revealed primary myelofibrosis with myeloid metaplasia (MMM). Their course was short with a blood picture similar to that of leukemia. They expired 2 mo. and 21/2 mo. after diagnosis, respectively. The cases were thought to represent an acute childhood variant of MMM. Cytogenetic study of circulating white cells by 24 h culture without phytohaemagglutinin stimulation revealed aneuploidy in both cases, the 1st case showing marked aneuploidy with a predominant karyotype of 50, XX, +8, +19, +19, +21 and the 2nd case a mosaic of 47, XX, +G/48, XX, +G, +G. The karyotype of phytohemagglutinin stimulated lymphocytes was 47, XX, +G in both cases. The abnormal karyotypes are those of circulating blastic cells which are abnormal clones of hematopoietic cells responsible for MMM. In Down''s syndrome, MMM might not be so rare as reported.