Genetics of Primary Hyperoxaluria

Abstract

Primary hyperoxaluria (PH) is a rare inborn error of metabolism characterized by increased production of oxalate and glycolate [1]. Urinary excretion of oxalate always exceeds 100 mg (1.1 mmol), and usually 200 mg (2.2 mmol) per day, as compared to less than 45 mg (0.5 mmol) in normals [1]. Elevated urinary excretion of oxalate not only leads to formation of calcium oxalate stones and to repeated attacks of renal colics, but also results in crystal deposition in the renal interstitium, which induces fibrosis and nephrocalcinosis. Renal damage, in turn, leads to oxalate retention and involvement of other organs, primarily of the bones, the arteries, the cardiac conduction system, the retina, and the neuromuscular system. Two types of PH have been described, of which type I (glycolic aciduria) is much more common than type II (L-glyceric aciduria) [2]. The discussion will therefore focus on PH type I. Apart from these two types, there appears to exist yet another variety of PH, in which the urinary excretion of both glycolate and glycerate are normal [3–5].