Clinical and molecular findings in three Moroccan families with distal renal tubular acidosis and deafness: Report of a novel mutation of ATP6V1B1 gene.

BACKGROUND: Primary distal renal tubular acidosis (dRTA) is a rare genetic condition characterized by an impaired acid excretion by the intercalated cells in the renal collecting duct. Recessive forms of this disease are caused by mutations in tow major genes: ATP6V1B1 and ATP6V0A4. Causal mutations in ATP6V1B1 gene are classically associated with early sensorineural hearing loss, however cases of tubular acidosis with early deafness have also been described in patients with mutations in the ATP6V0A4 gene. METHODS: The phenotype and genotype of three Moroccan consanguineous families with dRTA and deafness were assessed. Molecular analysis was performed by PCR amplification and direct sequencing of exon 12 of ATP6V1B1 gene. RESULTS: A novel c.1169dupC frameshift mutation of ATP6V1B1 gene was identified in one family and the c.1155dupC North African mutation in the tow other families. DISCUSSION AND CONCLUSION: In this report, we propose first line genetic testing based on screening of these two mutations both located in exon 12 of ATP6V1B1 gene in Moroccan patients with recessive form of dRTA associated to precocious hearing loss. Molecular diagnosis of dRTA leads to appropriate treatment and prevention of renal failure in affected individuals and to provide genetic counseling for families at risk.

Effects of automated peritoneal dialysis on residual daily urinary volume in children.

Preservation of residual renal function (RRF) is an important goal. In children, a more rapid decline in RRF has been observed under hemodialysis (HD) therapy as compared with peritoneal dialysis (PD) therapy. In adults, however, automated peritoneal dialysis (APD) may cause a more rapid decline of RRF than continuous ambulatory peritoneal dialysis (CAPD) does. The objective of the present study, a survey in a single center over the last 15 years, was to assess the impact of APD versus hemodiafiltration (HDF) on daily urinary volume (dUV) outcome. We included 97 children who were dialyzed for at least a 12-month period between January 1985 and December 1999, using either HDF (n = 60; 62%) or PD [n = 37; 38% (86% of those on APD)]. The endpoint was anuria occurrence, defined as a dUV below 50 mL/m2 body surface area (BSA) at three consecutive monthly determinations. Despite the use of HDF as hemodialysis therapy (that is, biocompatible membranes and a very low incidence of vascular instability during ultrafiltration), PD--even predominantly prescribed as APD--was associated with better preservation of residual dUV. At dialysis end, anuria occurred in 65% of the children undergoing HD as compared with 23% of those undergoing PD. The mean age of the children at dialysis start was lower in the PD group. No other significant differences were noted between the groups, either for the rate of uropathies or for the RRF at initiation of dialysis.