Antenatal diagnosis of cystinosis

Abstract

Cystinosis is a recessively inherited metabolic disorder characterized biochemically by a high intracellular content of free cystine; this results in cystine crystal deposition in many body organs. The primary genetic defect has not been identified. This disorder is diagnosable in cultured human skin fibroblasts and cultured amniotic fluid cells by radiochemically measuring the increased intracellular cystine levels, thus allowing antenatal detection of the disorder. Mrs P., who had had a previous child with cystinosis, presented at 16 wk gestation for antenatal diagnosis. Amniocentesis was performed, the amniotic fluid cells cultured for 6 wk, then 35 S-cystine was added to the culture medium of the test and control cells for 24 h. Mrs P.'s cultured amniotic fluid cells demonstrated elevated intracellular 35 S-cystine levels compared with the controls. Subsequently, the pregnancy was terminated. The diagnosis of cystinosis was confirmed by histopathological examination of fetal tissues and by elevated 35 S-cystine accumulation in cultured fibroblasts derived from the umbilical cord and pericardium of the abortus.