A 14-year-old mentally retarded boy with seizures who presented with severe thrombocytopenia, macrocytic anemia and allergic dermatitis after treatment with valproate for 12 years is reported from the University of Louvain Medical School, Brussels, Belgium. Serum valproate level was 48 mcg/ml. Bone marrow examination showed myeloblastic abnormalities. Recovery followed withdrawal of valproate. 
COMMENT. Thrombocytopenia is a well known side effect of valproate therapy. It is related to antibody-mediated platelet destruction, and tests for serum direct antiplatelet antibodies are positive. This report is unusual in the delayed occurrence of hematologic toxicity, even with relatively low serum levels of valproate.