Jacobsen syndrome, thrombocytopenia and humoral immunodeficiency.

Background - Clinical features of Jacobsen syndrome include facial dysmorph ism, congenital heart defects, digit anomalies and mild to moderate psychom otor retardation Thrombocytopenia or pancytopenia is observed in one half o f patients. Patients. - Two unrelated children, a 6-month- and a 12-year-old, presented with a moderate thrombocytopenia associated with the clinical features of Jacobsen syndrome. Bone marrow aspirates showed, in both patients normal ce llularity with an increased number of micromegacaryocytes. Chromosome analy sis showed a partial deletion of the long arm of chromosome 11. The 12-year -old patient had a history of upper respiratory airways infections with imm une humoral deficiency (decreased level of IgA and IgM) which, to our knowl edge, has never been reported. Conclusion. - Jacobsen syndrome is a cause of inherited thrombocytopenia in children. Humoral immune functions must be explored in patients with a his tory of repeated infections. (C) 1998 Elsevier, Paris.