48, XXYY syndrome associated with ethylenediaminetetraacetic acid (EDTA)-dependent pseudothrombocytopenia.

A 56-yr-old man with hypogonadism, gynecomastia, and mental retardation was evaluated for chromosome constitution and thrombocytopenia. Chromosomal analysis demonstrated the mosaicism of 48, XXYY and 47, XXY in the peripheral lymphocytes. Twenty out of twenty-five cells were 48, XXYY karyotype and the remaining five were 47, XXY karyotype. Thrombocytopenia was the EDTA-dependent pseudothrombocytopenia type 1 (platelet agglutination). Serological examination suggests that the platelet agglutinin belongs to IgM-kappa type. The present case exhibited both EDTA-dependent pseudothrombocytopenia and the 48, XXYY syndrome. Although this combination may have occurred purely by change, the possibility of whether or not the mosaicism of lymphocytes produces platelet agglutinin remains to be clarified.