Primary hyperoxaluria I, II, III types in children (review of literature)

   This review presents the latest data on the classification, pathogenesis, clinical and genetic features, and therapy of primary hyperoxaluria types I, II, and III in children with autosomal recessive inheritance. ORPHA portal of orphan diseases presents genes responsible for primary hyperoxaluria type I AGXT (93598); type II and type II GRHPR (93599), type III HOGA1 (93600). Worldwide genetic studies have established the pathogenesis, clinical phenotype and genotype features of primary hyperoxaluria. The pathogenesis of primary hyperoxaluria in children is based on impaired hepatic glyoxylate metabolism. The enzyme AGT catalyzes the conversion of L-alanine and glyoxylate to pyruvate and glycine, with vitamin B6 (pyridoxine) serving as a coenzyme for this reaction. Increased production of endogenous oxalate leads to increased blood oxalate concentrations and urinary oxalate excretion with the formation of renal calcium oxalate crystals and radiopaque concrements (calcium oxalate monohydrate – vevelite, calcium oxalate dihydrate – vedellite). High risk of progression to chronic kidney disease in primary hyperoxaluria in children of types I and II. Systemic oxalosis develops with increasing serum oxalate levels and the formation of calcium oxalate crystals with deposition in many organs and tissues. Therapy for primary hyperoxaluria in children includes: hydration (3l/m2/day) and citrates 100–150 mg/kg/day (potassium citrate 0.3–0.5 mmol/kg/day), pyridoxine at a dose of 5 to 20 mg/kg/day for vitamin B6 sensitive type I primary hyperoxaluria. Administration of oxalobacter formigenes and diet is effective. Combined liver and then kidney transplantation or simultaneous liver and kidney transplantation in patients with type I PH in B6-insensitive and isolated liver transplantation in B6-sensitive variants are performed. Timely molecular genetic testing in children with nephrocalcinosis makes it possible to establish a clinical and genetic diagnosis of type I, II, III PH, to carry out a personalised approach to treatment and to predict future health status.