Heterogeneity of patients with late onset ornithine transcarbamylase deficiency.

Fourteen patients, 10 males and 4 females, with "late onset" ornithine transcarbamylase (OTC) deficiency were diagnosed by enzyme assays performed on their liver tissues. Age of first clinical presentation ranged widely from 10 weeks to 23 y (mean = 6.1 y). Peak plasma ammonia levels varied widely from a low of 105 mumol/L to as high as 800 mumol/L. All patients had elevated plasma levels of glutamine whereas plasma levels of citrulline were normal in 6 patients. Plasma ornithine levels were not elevated in any patient. Orotic aciduria of variable degree was detected in 13 patients. Residual hepatic OTC activity was detectable in 13 out of the 14 patients ranging from 0.7 to 28.3 mumol/g/min (normal = 80.6 +/- 19.1, mean +/- SD, n = 52). Ten patients were alive at the time of this report and 5 of them had psychomotor delay.