A compound heterozygous mutation in the BSND gene detected in Bartter syndrome type IV

Bartter syndrome is a genetic disorder with hypokalemic metabolic alkalosis and is classified into five types. Type IV Bartter syndrome is a type of neonatal Bartter syndrome with sensorineural deafness and has been recently shown to be caused by mutations in the BSND gene. Owing to the rarity of this disease, only a limited number of mutations have been reported. We analyzed the BSND gene in a patient with type IV Bartter syndrome. The patient was delivered at 37 weeks, with normal body weight, and his neonatal course was uneventful. He was examined for developmental delay and polyuria at age 1 year 8 months and was found to have hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism, and sensorineural deafness. He developed end-stage renal failure at age 15 years, and renal transplantation was performed. We identified compound heterozygous mutations (Q32X and G47R) in the BSND gene. Each mutation was inherited from the parents. The Q32X mutation is a novel mutation and the first nonsense mutation identified in this gene. The mild perinatal clinical features of the patient were similar to those of a patient reported with a homozygous G47R mutation. However, the severity of renal failure suggested that factors other than this gene might affect the manifestation of renal abnormalities.