Primary distal renal tubular acidosis is a rare genetic disease. Mutations in SLC4A1, ATP6V0A4, and ATP6V1B1 genes have been described as the cause of the disease, transmitted as either an autosomal dominant or recessive trait. Particular clinical features, such as sensorineural hearing loss, have been mainly described in association with mutations in one gene instead of the others. Nevertheless, the diagnosis of distal renal tubular acidosis is essentially based on clinical and laboratory findings, and the series of patients described so far are usually represented by small cohorts. Therefore, a strict genotype-phenotype correlation is still lacking, and questions about whether clinical and laboratory data should direct the genetic analysis remain open. Here, we applied next-generation sequencing in 89 patients with a clinical diagnosis of distal renal tubular acidosis, analyzing the prevalence of genetic defects in SLC4A1, ATP6V0A4, and ATP6V1B1 genes and the clinical phenotype. A genetic cause was determined in 71.9% of cases. In our group of sporadic cases, clinical features, including sensorineural hearing loss, are not specific indicators of the causal underlying gene. Mutations in the ATP6V0A4 gene are quite as frequent as mutations in ATP6V1B1 in patients with recessive disease. Chronic kidney disease was frequent in patients with a long history of the disease. Thus, our results suggest that when distal renal tubular acidosis is suspected, complete genetic testing could be considered, irrespective of the clinical phenotype of the patient

Long term follow-up from this large dRTA cohort shows an overall favourable outcome with normal adult height for most and no patient with CKD 5. Yet, 82% of adult patients have CKD 2-4. Importance of adequate metabolic control was highlighted by better growth and renal function but was achieved in only half of patients.

Secondary hyperparathyroidism contributes to post-transplant CKD mineral and bone disorder. Paricalcitol, a selective vitamin D receptor activator, decreased serum parathyroid hormone levels and proteinuria in patients with secondary hyperparathyroidism. This single-center, prospective, randomized, crossover, open-label study compared the effect of 6-month treatment with paricalcitol (1 mg/d for 3 months and then uptitrated to 2 mg/d if tolerated) or nonparicalcitol therapy on serum parathyroid hormone levels (primary outcome), mineral metabolism, and proteinuria in 43 consenting recipients of renal transplants with secondary hyperparathyroidism. Participants were randomized 1:1 according to a computer-generated sequence. Compared with baseline, median (interquartile range) serum parathyroid hormone levels significantly declined on paricalcitol from 115.6 (94.8-152.0) to 63.3 (52.0-79.7) pg/ml (P,0.001) but not on nonparicalcitol therapy. At 6 months, levels significantly differed between treatments (P,0.001 by analysis of covariance). Serum bone-specific alkaline phosphatase and osteocalcin decreased on paricalcitol therapy only and significantly differed between treatments at 6 months (P,0.001 for all comparisons). At 6 months, urinary deoxypyridinoline-to-creatinine ratio and 24-hour proteinuria level decreased only on paricalcitol (P,0.05). L3 and L4 vertebral mineral bone density, assessed by dual-energy x-ray absorption, significantly improved with paricalcitol at 6 months (P,0.05 for both densities). Paricalcitol was well tolerated. Overall, 6-month paricalcitol supplementation reduced parathyroid hormone levels and proteinuria, attenuated bone remodeling and mineral loss, and reduced eGFR in renal transplant recipients with secondary hyperparathyroidism. Longterm studies are needed to monitor directly measured GFR, ensure that the bone remodeling and mineral effects are sustained, and determine if the reduction in proteinuria improves renal and cardiovascular outcomes.

Introduction: Vitamin D receptor activator (VDRA) therapy has been shown to be associated with reduced mortality rates in chronic kidney disease (CKD) patients with secondary hyperparathyroidism (SHPT). However, differences between VDRAs in their ability to reduce both all-cause and cardiovascular-related mortality rates are not yet fully elucidated. Methods: The objective of the current analysis was to determine the effect of VDRA therapy on mortality in an Italian dialysis population, observed prospectively every 6 months for 18 months. Patients were investigated for all-cause and cardiovascular-related mortality risk adjusted for various demographic, clinical, and/or SHPT treatment variables. Results: The cumulative probabilities of all-cause and cardiovascular-related mortality were lower for patients who received any VDRA treatment compared with those who did not (p < 0.001) regardless of all measured variables. Additionally, patients who received paricalcitol and/or cinacalcet (with or without VDRAs) compared with calcitriol showed a significant improvement in both all-cause and cardiovascular-related mortality (p < 0.001). Cinacalcet with or without VDRAs was not associated with a further decrease of mortality hazard ratios compared with paricalcitol monotherapy. Conclusions: VDRA therapy (associated or not with cinacalcet) was associated with improved survival in dialysis patients, independent of demographic and clinical variables.

These observations, including a previous description of a similar case in the literature, indicate that MSK could be a consequence of the proton pump defect, thus can potentially provide new insights into the pathogenesis of MSK.