Misdiagnosis of chronic thrombocytopenia in childhood

PURPOSE: Children ultimately diagnosed with nonimmune chronic thrombocytopenia are often referred to pediatric hematology clinics with a provisional diagnosis of autoimmune thrombocytopenic purpura (AITP). The authors' aim was to establish in these patients the features characterizing the mechanism of thrombocytopenia. PATIENTS AND METHODS: The authors performed a retrospective review of the case records of seven children (three boys and four girls, aged 5 months to 7 years) with misdiagnosed chronic AITP referred to a single pediatric hematology center between 1990 and 2000. RESULTS: In the seven children, the suspected diagnosis on referral was AITP and the final diagnosis was inherited thrombocytopenia. Abnormalities of platelets and/or leukocyte morphology were present in all of them. Other features suggestive of inherited thrombocytopenia included a history of familial thrombocytopenia (2/7), failure of steroids and/or intravenous immunoglobulins to raise the platelet count to normal levels (5/7), and moderate increase of Indium-111 platelet turnover in the two patients tested. Platelet-associated IgG (PaIgG) was above the normal threshold in the four children tested; the direct monoclonal antibody immobilization of platelet antigens (MAIPA) test was negative in the four children tested and the serum test was positive in two boys. Bone marrow examination revealed either a normal (4/7) or an elevated (3/7) number of megakaryocytes. CONCLUSIONS: Family history and blood cell morphology analysis in experienced hands are the first steps in discriminating AITP from inherited thrombocytopenia in children with isolated chronic thrombocytopenia. In contrast, bone marrow examination and search for specific autoantibodies using the MAIPA test are of little help. An isotopic platelet life span study, when available, should be performed before considering splenectomy to exclude the diagnosis of inherited thrombocytopenia, especially when steroids and/or IgG IV administration failed to raise the platelet count.