Paroxysmal nocturanal hemoglobinuria and marrow failure treated by infusion of marrow from an identical twin.

An 18-year-old white Canadian male patient with paroxysmal nocturnal hemoglobinuria and refractory marrow failure received a marrow infusion from his normal identical twin brother without prior ablation of the patient's marrow by drugs or irradiation. After 2 years of follow-up, the patient is well with no evidence of clinical disease or significant hematological abnormality. The results suggest that normal marrow stem cells can have a selective advantage over the abnormal paroxysmall nocturnal hemoglobinuria clone.