RHBG and chronic kidney disease: The present study aims to identify in CKD patients, loss of function mutations in RhBG, one of the NH<sub>3</sub>/NH<sub>4</sub> <sup>+</sup> transporters in the collecting duct, and to show that NH<sub>3</sub>/NH<sub>4</sub> <sup>+</sup> transport is impaired by these mutations.