963 IMMUNODEFICIENCY IN A CHILD WITH A HEALTHY ADENOSINE DEAMINASE DEFICIENT MOTHER

Abstract

We recently studied a 27 year old woman with adenosine deaminase (ADA) deficiency. Red cell lysates exhibited less than 1 μmole/g hgb/hr conversion of either adenosine or deoxyadenosine to inosine. Lysates made from peripheral blood lymphocytes showed less than 0.5 nmoles/min/mg protein utilization of adenosine. Studies employing intact lymphocytes demonstrated conversion of [8-14C]-adenosine to [8-14C] inosine and [8-14C] hypoxanthine proceeded at 10-20% of the rate of normal lymphocytes. Mixing experiments with red cell extracts failed to demonstrate an inhibitor. She has produced 3 children, one of whom expired with ADA deficient severe combined immunodeficiency. This child's disease was somewhat atypical in that she had considerable lymphoid tissue and the gross and microscopic features of the thymus were relatively normal in appearance and cytology at autopsy. Her husband and 2 living children had approximately half normal ADA activity in their red cell lysates. Starch gel electrophoresis of these lysates indicated the presence of the ADA 1 phenotype. No consanguinity could be detected in the family. Although an absolute determination of the genetics of this disease in this family was not possible, the most likely explanation is that the mother is homozygous for a low activity ADA variant while the father is heterozygous for a more common form of ADA deficiency.