Several deafness genes are not categorized but are ubiquitously expressed in the inner ear and play important functional roles. Disorders in these genes can result in hearing loss. These genes include WFS1, COCH, TMPRSS3, GSDME, CRYM, and mitochondrial genes. Wolframin, encoded by WFS1, plays a key role in endoplasmic reticulum (ER) function. Pathogenic variations in the Wolfram syndrome type 1 gene (WFS1) cause a wide range of disorders, including ADNSHL, DFNA6/DFNA14/DFNA38 (MIM #600965), Wolfram-like syndrome (WLS) (MIM#614296), and more severe types of autosomal recessive disorder Wolfram syndrome type 1 (WS1) (MIM #222300). The COCH gene encodes a protein called cochlin, the most abundant protein in the extracellular matrix of the inner ear, which plays a number of crucial roles, including maintaining structural integrity of the inner ear, regulating the extracellular matrix composition, and providing a protective function. Pathogenic variations in COCH are associated with DNFA9, often accompanied by balance problems. TMPRSS3 (transmembrane protease, serine 3) is essential for cochlea function and development, particularly the maintenance and survival of cochlear hair cells. Pathogenic variants in TMPRSS3 cause non-syndromic hearing loss, DFNB8 or DFNB10. GSDME, abundantly expressed in the cochlea, is primarily involved in regulated cell death. Pathogenic variants in GSDME cause a toxic gain of function, resulting in progressive hearing loss (DFNA5). CRYM (crystallin mu), the second most commonly expressed gene in the human cochlea after COCH, encodes protein mu-crystallin, which is responsible for thyroid hormone binding and metabolism in the inner ear. Pathogenic variants in CRYM lead to autosomal dominant non-syndromic hearing loss, DFNA40. Mitochondrial gene variants have been found to cause syndromic and non-syndromic sensorineural hearing loss. The m.3243A>G variant is one of the most common mitochondrial variants known to cause syndromic hearing loss. It has been reported to be associated with a wide range of diseases, such as MIDD (maternally inherited diabetes and deafness) and MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes). Non-syndromic hearing loss due to m.1555A>G in the MT-RNR1 gene is also commonly encountered in clinical outpatient clinics. It is known to be related to aminoglycoside antibiotic-induced hearing loss.