Severe manifestation of Bartter syndrome Type IV caused by a novel insertion mutation in the BSND gene

Bartter syndrome Type IV is a rare subtype of the Bartter syndromes that leads to both severe renal salt wasting and sensorineural deafness. This autosomal recessive disease is caused by mutations in the gene encoding barttin, BSND, an essen- tial subunit of the ClC-K chloride channels expressed in renal and inner ear epithelia. Patients differ in the severity of renal symp- toms, which appears to depend on the modi- fication of channel function by the mutant barttin. To date, only a few BSND mutations have been reported, most of which are mis- sense or nonsense mutations. In this study, we report the identification of the first inser - tion mutation, p.W102Vfs*7, in the BSND gene of a newborn girl with acute clinical symptoms including early-onset chronic re- nal failure. The results support previous data indicating that mutations that are predicted to abolish barttin expression are associated with a severe phenotype and early onset re- nal failure.