715 THYMIC APLASIA IN SIBLINGS

Abstract

DiGeorge syndrome is usually reported as having occurred sporadically. This is the first report of the syndrome occurring in twins and only the second in family members. Black male twins were delivered at 33 weeks gestation. They were dizygotic as proven by different blood types. Each developed hypocalcemic seizures at 9 days. The diagnosis of DiGeorge syndrome was made in each on the basis of refractory hypocalcemia, typical facial features, absent thymic shadow, congenital heart disease and repeatedly low T-cell rosettes with normal immunoglobulins. One died at 58 days of age of aspiration and congestive heart failure. He was found at autopsy to lack thymic tissue and parathyroids. His heart disease consisted of a hypoplastic ascending aorta with the right subclavan artery arising from the right pulmonary artery. The other twin, now 3 yrs. old, has serially low T-cell rosettes, normal PHA stimulation and normal immunoglobulins. He does not suffer from recurrent infections nor does he require calcium or parathormone supplementation. Clinically, he has a small VSD. He is now less than the 3rd percentile in both height and weight and is developmentally delayed. Maternal evaluation revealed normal calcium, phosphorus and parathormone levels. Antilymphocyte antibodies were absent. Although DiGeorge syndrome is usually sporadic, the occurrance in nonidentical twins suggests a genetic etiology in this family.