P0172ARE FREQUENT STONE REMOVAL PROCEDURES IN PATIENTS WITH PRIMARY HYPEROXALURIA TYPE 3 (PH 3) RELATED TO DECLINE IN KIDNEY FUNCTION?

Abstract

Abstract Background and Aims PHIII is seen as the less problematic type of autosomal recessive inherited PH. This group of disorders in glyoxylate metabolism is clinically characterized by recurrent urolithiasis and/or progressive nephrocalcinosis, and, in type I and II, end-stage renal failure. The cause of PHIII was identified only in 2010 and unlike in PHI/II a remarkable low prevalence of symptomatic adults was observed, hence long-term clinical data are scarce. This phenomenon is commonly attributed to reduced penetrance of causative hydroxy-oxo-glutarate aldolase 1 gene (HOGA1) variants and a still unexplained tendency for clinical remission with age. Most PHIII patients present in early childhood with recurrent urolithiasis and undergo (repeated) stone removal procedures. We now hypothesized that repeated stone removal procedures may be associated with decline in kidney function. Method We retrospectively analyzed clinical and laboratory data of 41 genetically confirmed PHIII patients (0.5-29.3 years of age, with (20 different) biallelic mutations in the HOGA1 gene). Period of follow-up ranged from just diagnosed to 22 years. Results Recurrent urolithiasis was most prominently found in the first 3 years of life (>25% of patients). Not all patients experienced clinical remission, 3/6 patients > 20 years of age have ongoing kidney stone development. In addition, patients presented with nephrocalcinosis and/or urolithiasis. A high amount of stone removal procedures during the first years, but also later in life was observed. Urinary oxalate excretion is significantly elevated, and within the range of PHI/II. A decline in kidney function was observed, which is related to a decreased clearance of oxalate (figure). Two patients each post multiple stone removal procedures had CKD stages 2 or 3. Seven further patients had CKD stage 2, which was not related to stone removal. Conclusion PHIII is said to be the most favorable PH type, but early diagnosis is mandatory to treat the patients adequately and to avoid repeated stone removal procedures, which may have an influence on decline in kidney function. This decline may also be related to hyperoxaluria per se, as reported for PHI and II.