Successful nonsibling bone marrow transplantation in severe combined immunodeficiency

Attempted reconstitution of a foal with primary severe combined immunodeficiency

A foal with primary severe combined immunodeficiency, diagnosed within the first two weeks of life, was maintained with its dam in semi-isolation. The foal received continuous prophylactic antibiotic therapy, plasma from a sibling hyperimmunised with equine adenovirus vaccine, and intensive general nursing care. A full sibling female was selected as a bone marrow donor on the basis of red blood cell cross-matching and mixed lymphocyte reactions. Cyclophosphamide was given before two bone marrow transfusions at 35 and 73 days of age. To prevent graft versus host disease graft versus host disease the foal was maintained on methotrexate therapy. Reconstitution was not achieved nor were there signs of graft versus host disease. The foal died suddenly four days after the second bone marrow transfer when 77 days old. It had remained clinically free of any life threatening infectious disease and at necropsy a remarkable degree of freedom from infectious disease was confirmed. The most notable necropsy findings were bilateral nephrosis and myocardial degeneration and fibrosis. The likely cause of death was an electrolyte imbalance, particularly hypokalaemia, which secondarily affected the myocardium. Renal toxicity caused by the cytotoxic drugs, especially cyclophosphamide, may have contributed to the electrolyte imbalance.

Histocompatibility testing for clinical bone marrow transplantation and prospects for identification of donors other than HLA genotypically identical siblings

Clinical histocompatibility testing has now developed to a stage where it is possible to select related bone marrow donors for some patients, when HLA genotypically identical siblings are not available. The most common type of such donors are the HLA phenotypically or HLA-D phenotypically identical related donors. The HLA-D homozygous recipient offers special options, since these patients can potentially receive bone marrow transplants from any of the parents or from HLA-haploidentical siblings. The studies in SCID have demonstrated that HLA-D compatibility in spite of HLA-A or B incompatibilities can be tolerated and there is now accumulating evidence that even patients with aplastic anemia or acute leukemia can be successfully treated with such bone marrow grafts.