Early cystinuria, a risk factor for metabolic urolithiasis.

The levels of urinary amino acids (cystine, amino acids with basic character, branched chain amino acids and phenylalanine) were determined in the 24 hr urines of 5,500 newborns and in 20 subjects ranging in age from 2.5 to 20 years, with a suspicion of metabolic diseases. Seven newborns have shown a biochemical pattern of cystinuria. The urinary cystine levels in the first days of life appeared to correlate with an increased risk of developing, at the adult age, metabolic mono- or bilateral urolithiasis.