PPIB and Bartter syndrome type 4: BSND encodes the β-subunit of ClC-K chloride channels, which play an important role in chloride transport in the kidney and inner ear.40 Germline mutations of the BSND gene cause Bartter syndrome type IV, which is an autosomal recessive disease characterized by salt loss, hypokalemia, metabolic alkalosis, and sensorineural deafness.41 At present, several research papers examining germline mutations of the BSND gene in the Bartter syndrome family have been reported;42 however, the expression of BSND protein in RCC has not been previously reported.