#4989 FIRST INTERIM ANALYSIS OF THE INTERNATIONAL DISTAL RENAL TUBULAR ACIDOSIS REGISTRY

Abstract Background and Aims Primary Distal Renal Tubular Acidosis (dRTA) is a rare genetic condition characterized by impaired capacity of A-type intercalated cells to excrete excess of H+ ions. The disease is caused primarily by pathogenic variants in the SLC4A1 gene encoding for the basolateral anion exchanger 1 (AE1) or the ATP6V1B1 and ATP6V0A4 genes encoding for two subunits of the apical proton ATPase. The latter also cause variable degrees of sensorineural hearing loss (SNHL). Additional genes include WDR72 that is associated with amelogenesis imperfecta and FOXI1 that also causes SNHL. To understand better the impact of alkali treatment on the natural history of dRTA, a European prospective registry has been created in collaboration with the ERKNet European Reference Network. Method We present a first interim descriptive analysis of first 182 patients that have been collected from 2019 to 2022. Treatment data are under analysis and are not included. Results To date, mostly paediatric patients (79%) have been included in the registry. A genetic diagnosis was available in 111/182 (61%) of patients and showed the following distribution of underlying genes: ATP6V0A4: 45%, ATP6V1B1: 41%, SLC4A1: 14%. Variants in WDR72 and FOXI1 were reported in one patient each. Overall, we observed no major differences in blood pressure and in urinary/blood parameters, when comparing children vs adults or proton ATPase vs AE1 defects (partially shown in tables 1 and 2). Adult patients were on average diagnosed later, had more frequently nephrolithiasis and higher BMI. In part, differences may reflect selections biases that will be assessed with the collection of longitudinal data. As expected, patients with proton pump defects were diagnosed earlier and had more frequently SNHL. The degree of nephrocalcinosis and the estimated glomerular filtration rates were similar when comparing all groups. None of the patients had developed end stage kidney disease. Conclusion This first report demonstrates successful enrolment of a cohort of patients with dRTA. Enrolment is still ongoing. Longitudinal data will allow assessing the impact of alkali therapy on the long-term outcome.