PRENATAL DIAGNOSIS OF NEPHROPATHIC CYSTINOSIS: Pregnancy at Risk Ascertained through Heterozygote Diagnosis of Parents

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Abstract
The biochemical diagnosis of cystinosis in a deceased girl was made indirectly through the demonstration of heterozygote values of free-cystine contents in leukocytes from both parents. Amniocentesis was performed on the mother in the 16th wk of 2 subsequent pregnancies. Amniotic fluid cell lysate from the 1st fetus had 6-8 times normal levels of radioactivity in the cystine band determined by a 35S-cystine pulse labeling method followed by high voltage electrophoresis on paper. Values for the cystine contents in various organs of the affected fetus are given. The 2nd fetus was unaffected; this was subsequently confirmed by the birth of a healthy child. The results of the laboratory analyses in these 2 cases were available to the parents 21 and 23 days following amniocentesis, respectively. The interruption of the 1st pregnancy was performed in the 19th wk. This was 4 and 6 wk earlier, respectively, than in the 2 previously reported induced abortions of affected fetuses, and should increase the acceptability of the present method for prenatal diagnosis of nephrophatic cystinosis.