Argininosuccinic aciduria: clinical and biochemical findings in three children with the late onset form, with special emphasis on cerebrospinal fluid findings of amino acids and pyrimidines.

Three children with the late onset form of argininosuccinic aciduria are presented. The first two are sisters. The clinical features are characterized by mild retardation and ataxia, complicated by episodes of hyperammonemia. All patients showed elevated concentrations of argininosuccinic acid and its anhydrides in all body fluids, most pronounced in cerebrospinal fluid (CSF). Moreover, in Cases 1 and 2, we found elevated concentrations of pseudouridine and uridine limited to CSF, which was not reported before. In Case 3, with some residual activity of argininosuccinate lyase (ASL), we found normal values of these compounds. In urine we found elevated concentrations of uracil in Cases 1 and 2, and orotic acid in Case 2. Plasma showed an elevated concentration of orotic acid in all three patients, uracil was elevated in Case 2, cytidine was elevated in Cases 2 and 3. The results are being discussed and indicate that CSF values of pyrimidines reveal new biochemical abnormalities of brain tissue in urea cycle disorders.