Genetic mutation is one of the causative factors for idiopathic progressive hearing loss. A patient with late-onset, moderate, and high-frequency hearing loss was found to have a novel, heterozygous KCNQ4 mutation, c.806_808delCCT, which led to a p.Ser260del located between S5 and the pore helix (PH). Molecular modeling analysis suggested that the p.Ser269del mutation could cause structural distortion and change in the electrostatic surface potential of the KCNQ4 channel protein, which may impede K+ transport. The present study supports the idea that a non-truncating mutation around the N-terminus of PH may be related to moderate hearing loss. (C) 2013 Elsevier Inc. All rights reserved.