CPS1 and hyperinsulinemic hypoglycemia, familial, 4: Diagnosis may be further refined by enzyme analysis in appropriate tissues as follows: liver biopsy (CPS-1, N-acetyl glutamate synthetase, and OTC deficiencies); red blood cells (arginase deficiency); and fibroblasts (skin biopsy, argininosuccinic acid synthetase and argininosuccinic acid lyase deficiencies).