Neonatal argininosuccinic aciduria with normal brain and kidney but absent liver argininosuccinate lyase activity.

An infant is described who died at 6 days of age with hyperammonemia and argininosuccinic acid in the urine. Argininosuccinic acid lyase (AL) was absent in liver, decreased in red blood cells, but normal in brain and kidney. The instability of AL in frozen stored tissues accounts for previous reports of deficient AL activity in the brain and kidney of neonates with this disease. The variation of AL activity in the tissues of this patient demonstrates that more than one gene locus either codes for the structure of this enzyme or regulates its biosynthesis in different organs.