Studies using mouse models of human Pendred syndrome/DFNB4 have revealed that SLC26A4 dysfunction disrupts ion transport in MRCs of the endolymphatic sac, preventing normal endolymph absorption in the embryonic inner ear, which consequently leads to dilated endolymphatic space, EVA, and endolymph acidification [6,7]. The gene discussed is SLC26A4; the disease is Pendred syndrome.