Amino acid patterns in cystinuric families.

The delineation of cystinuria into two types, 'recessive' and 'incompletely recessive', according to a differential expression of the gene defect in carriers by urinary parameters (Harris et al., 1955a, b), has been further refined into three forms by including in phenotype analysis evidence for heterogeneity (Rosenberg, 1966; Rosenberg et al., 1966) of the accompanying intestinal transport defect in stone formers (Asatoor et al., 1962; Milne et al., 1961). Thus, the 'recessive' of Harris resembles the Type I form of Rosenberg, in which the stone formers lack active transport systems in the gut for cystine and the basic amino acids, and the carriers excrete normal amounts of these amino acids; the 'incomplete recessives' fall into either Type III without the intestinal defect in the stone formers and with intermediate levels ofexcess excretion by the carriers, or into Type II with a partial transport defect and with grosser excretory excesses by the carriers. Our report describes the amino acid excretion of 35 members of three cystinuric families*, attempts to classify the gene defects by urinary parameters only, and evaluates the excretion of the disulphide, cysteine-homocysteine (Frimpter, 1961, 1963), as a key to the carrier state.