New aspects of infantile oxalosis.

Infantile oxalosis is the most severe form of primary hyperoxaluria type I (PH I). Only 28 patients have been reported in detail; it was found that diagnosis was usually delayed, and most patients presented before the age of 4 months in renal failure and died within the 1st year of life. This report comprises two infants in whom diagnosis of PH I was made in the first few weeks of life before renal function was impaired. Case 1, whose brother had died of infantile oxalosis, already had greatly increased urinary oxalate and glycolate excretion at 7 days of age. In Case 2, PH I was diagnosed early because of the finding of increased renal echogenicity at 3 weeks of age; this patient had numerous episodes of stone formation despite continuous treatment with pyridoxine, but maintained renal function with normal serum creatinine levels at the age of 28 months. Prenatal diagnosis was attempted in case 1; however, amniotic fluid oxalate and glycolate concentrations were normal, suggesting that these acids pass the placenta and are not retained. The recent discovery of a transamination defect (deficiency of the peroxisomal enzyme alanine: glyoxylate aminotransferase) explains why some patients respond to pyridoxine treatment. Differences in onset and severity of PH I and in response to pyridoxine suggest that this disorder is biochemically and genetically heterogeneous.