49, XXXXY syndrome with unilateral renal aplasia, proteinuria, and venous thromboembolism.

A 28-year-old man presented with mental retardation, peculiar facial features, radioulnar synostosis, hypogonadism, aplasia of the right kidney, a moderate degree of proteinuria, and peripheral cyanosis. The activated partial thromboplastin time was shortened, and the level of plasma factor VIII was high. A chromosomal analysis revealed a 49, XXXXY karyotype. From the 10th hospital day, he suffered from sudden dyspnea following swelling of the left leg. He was diagnosed as having deep vein thrombosis and pulmonary embolism, and was successfully treated with anticoagulant therapy. This is the first case of the 49, XXXXY syndrome complicated with unilateral renal aplasia, proteinuria, and venous thromboembolism.