OTOF-related deafness is characterized by two phenotypes: prelingual nonsyndromic auditory neuropathy spectrum disorder (ANSD) and, less frequently, temperature-sensitive auditory neuropathy spectrum disorder (TS-ANSD). OTOF-related ANSD is characterized by congenital or prelingual, typically severe-to-profound bilateral deafness without inner-ear anomalies on MRI or CT examination of the temporal bones. Otoacoustic emissions (OAEs) are present and auditory brain stem response is abnormal at birth. Newborn hearing screening testing of OAEs only will fail to detect this disorder in most individuals. OAEs may decrease or disappear with age in 20%-80% of individuals. TS-ANSD typically presents with normal-to-moderate hearing loss (0-55 dB) at baseline body temperature. An elevation of body temperature (approximately 0.5°C or more) triggers significant bilateral hearing loss ranging from severe to profound, with resolution of hearing loss typically occurring within hours of a return to baseline body temperature.

Auditory neuropathy is a type of hearing loss defined by the preservation of cochlear outer hair cell function and abnormal or absent auditory brainstem responses. Auditory neuropathy may accompany peripheral neuropathy in a variety of dominant syndromes such as Charcot-Marie-Tooth disease (Satya-Murti et al., 1979) and has been observed in Friedreich ataxia (Satya-Murti et al., 1980). Auditory neuropathy unassociated with peripheral neuropathy most commonly occurs as a sporadic or recessive trait; see, for example, 601071. Genetic Heterogeneity of Autosomal Dominant Auditory Neuropathy See also AUNA2 (620384), caused by mutation in the ATP11A gene (605868) on chromosome 13q34, and AUNA3 (619832), caused by mutation in the TMEM43 gene (612048) on chromosome 3p25.

Combined oxidative phosphorylation deficiency-54 (COXPD54) is an autosomal recessive disorder with pleiotropic multisystem presentations resulting from a disruption in mitochondrial transcription and translation. The phenotype is highly variable. Many patients have early-onset sensorineural hearing loss, sometimes in isolation, and sometimes associated with global developmental delay or primary ovarian failure. Other features may include peripheral hypertonia, seizures, muscle weakness, behavioral abnormalities, and leukoencephalopathy on brain imaging. Serum lactate may or may not be elevated (summary by Hochberg et al., 2021). For a discussion of genetic heterogeneity of combined oxidative phosphorylation deficiency, see COXPD1 (609060).