Argininosuccinic aciduria: investigation of an affected family.

Two siblings with argininosuccinic aciduria were studied by an interdisciplinary team. Considerable variability in the clinical expression of this disorder was observed in comparison with previously reported cases. Detection of the heterozygous state in the parents and in a fetal sibling was demonstrated by tissue assay for argininosuccinase activity. Mental retardation and neurologic deficits in the affected children were irreversible with dietotherapy but growth was progressive and the general course was relatively benign.