THE METABOLIC DEFECT RESPONSIBLE FOR URIC ACID STONE FORMATION *

The composition of a urinary tract stone often may be related to increased urinary concentration of one or more of the stone constituents or to characteristic hydrogen ion concentrations in the urine (1). Thus calcium phosphate and calcium oxalate are the major constituents of stones in patients with hypercalciuria, cystine stones are limited to patients with increased urinary cystine due to cystinuria (2), and calcium magnesium am-monium phosphate stones are generally found in patients with constantly alkaline urine due to urea-splitting infections. Boyce and King (3) have suggested that formation of an organic matrix may be the primary abnormality in stone formers and that the mineral content of the stone may reflect merely the chemical composition of the urine at the time the matrix was formed. This paper con-cerns studies of certain chemical factors in patients known to form uric acid stones. Uric acid stones occurred in 10 per cent of a series of 207 stone patients (1). As a group these patients presented certain clinical characteristics. Thus, of 67 consecutive uric acid stone patients, the average age was 59, which is considerably older than the average age of the other groups of stone patients (1). Of these 67 patients 42 were male and 15 female. Fifty per cent of this series was Italian or Jewish, in contrast to 14 per cent Italian or Jewish among 77 miscellaneous stone patients for whom no cause of stone was identified (1). Uric acid stones have the same radiodensity as soft tissues, are unapparent in plain roentgeno