Arginine deficiency syndrome. Its occurrence in carbamyl phosphate synthetase deficiency

A child with carbamyl phosphate synthetase deficiency was studied. During attempts at dietary control, a peculiar rash and cessation of growth were noted concomitant with a very low serum arginine level. A prospective study was designed so that the only variable would be the addition of 400 mg of arginine to his diet. During the two-week period without arginine, the rash and growth failure recurred and paralleled a drop in the serum arginine level from 0.048 to 0.034 nmol/mL. Then with the addition of arginine, his rash dramatically cleared and he resumed normal growth. Later, it became necessary to raise his arginine intake to 800 mg/day to maintain continued growth. These data support the concept that arginine becomes an "essential" amino acid in persons with urea cycle defects, which may partially explain the extremely variable clinical manifestations and courses seen in these patients.