Primary hyperoxaluria type 2.

Primary hyperoxaluria type 2 (PH2) is a rare disease with only 24 patients reported in the literature so far. It should be considered in any patient presenting with urolithiasis or nephrocalcinosis due to hyperoxaluria. The metabolic defect is deficiency of D-glycerate dehydrogenase/glyoxylate reductase leading to characteristic hyperoxaluria and excretion of L-glycerate, the cornerstone of diagnosis of PH 2. Although development of terminal renal failure seems to be less prevalent than in PH 1, recent reports indicate that chronic as well as terminal renal insufficiency may occur. Therefore specific therapeutic measures should aim at reduction of urinary calcium oxalate saturation by potassium citrate or pyrophosphate to reduce the incidence of nephrolithiasis and nephrocalcinosis and thus improve renal survival. Secondary complications (obstruction, urinary tract infections and pyelonephritis) must be avoided. In patients with terminal renal failure isolated renal transplantation seems to carry a high risk of disease recurrence.

CONCLUSIONS

PH 2 is a rare but important cause of urolithiasis and nephrocalcinosis; long-term follow up is necessary, since the renal prognosis may be worse than previously anticipated.