Severe regimen-related toxicity occurring in a patient with XYY syndrome receiving allogeneic peripheral blood stem cell transplantation.

A 23-year-old man with chronic myelocytic leukemia (CML) in the first chronic phase underwent allogeneic peripheral blood stem cell transplantation (PBSCT) from his HLA-identical sibling. Pretransplant evaluations showed that he had a low risk of transplantation-related mortality and that the interval between the diagnosis of CML and PBSCT was only 6 months. However, he developed a variety of complications, including acute renal failure requiring hemodialysis, severe hepatic damage, hemorrhagic cystitis, and gastrointestinal hemorrhage leading to hypovolemic shock. Pathological examination of the colonic mucosa showed vascular endothelial damage and thrombotic lesions, leading to the diagnosis of thrombotic microangiopathy. Later, we found that he had the constitutional abnormality XYY. XYY syndrome is a frequent congenital abnormality, and mental disorders and congenital abnormalities of kidney and liver are common manifestations. Considering his clinical course, it was interesting that complications were severe in the organs which are frequently involved in cases of XYY syndrome. These organs may have poor function or poor reserves and may be more vulnerable to endothelial damage caused by high-dose cytotoxic chemotherapy. Patients with XYY syndrome might have a high risk of transplantation-related mortality.