Hearing Impairment and Pigmentary Disturbance^a

Abstract

Hearing impairment is a variable manifestation of several heritable conditions in which pigmentation of the skin or eyes is abnormal. Some of these disorders are well recognized although uncommon, while others are virtually private syndromes. Practical issues concerning the major conditions of this type are reviewed in this article on a basis of a survey of 4452 profoundly deaf children attending special schools in Southern Africa, together with investigations in affected families. The Waardenburg syndrome (WS), which is the most common deafness-depigmentation disorder, was present in 121 (2.7%) of the 4452 deaf scholars. Further studies in 7 multigeneration affected families confirmed phenotypic variability and indicated a need for internationally agreed diagnostic criteria. In 4 Cape Town families of mixed ancestry the WS-I gene was linked to the 2q37 locus, but in another large kindred no linkage could be demonstrated. Nonallelic heterogeneity is possible. There is uncertainty concerning possible interrelationship between WS and piebaldism. The phenotypic consistency of a South African family in which 7 persons in 3 generations had gross piebaldism in the absence of disturbance of hearing or involvement of the eyes and periorbital structures is suggestive that this disorder and WS are separate entities. Molecular investigations indicate that the gene for piebaldism in this kindred is not situated at the WS-I locus 2q37. Deafness and hyperpigmentation are present in neurofibromatosis type II (acoustic neuromata) and the multiple lentigines syndrome, while retinal pigmentation is a feature of the Usher syndrome. This latter entity is apparently much less common in Southern Africa than in other parts of the world.

Melanin precursors prevent premature age-related and noise-induced hearing loss in albino mice

“…Hence, these cells are essential for hearing and accordingly, genetic deficiencies in melanocytes produce hearing impairment in mice and humans. For example, mutations in the human MITF locus cause the Waardenburg syndrome type IIA (Beighton et al., 1991;Saito et al., 2003; Tassabehji et al., 1994), whereas mutations in the homologous mouse Mitf locus also cause sensorineural deafness (Steingrímsson et al., 1994).…”

Feline Deafness

“…7). This deafness mimics the Scheibe deformity of humans [5,51–53], which features early postnatal onset of sensorineural hearing impairment that is transmitted in an autosomal dominant pattern with incomplete penetrance [5,36,54–56].

Blue-eyed white cats can have what is called cochleosaccule degeneration, causing profound deafness.

White cats can also exhibit “spongioform” degeneration of the internal ear, also causing deafness.

White cats are not necessarily albino cats.

…”

Synaptic morphology and the influence of auditory experience

“…That is, the deafness is apparently caused by a collapse of Reissner’s membrane, which obliterates the scala media and the organ of Corti (Scheibe, 1882,1885; Bosher and Hallpike, 1965,1967; Deol, 1970; Suga and Hattler, 1970; Mair, 1973; Brighton et al, 1991). The question could be asked whether the synaptic changes observed in these deaf cats are due to loss of neural activity in the auditory nerve, or whether they are part of the genetic syndrome and unrelated to spike activity.…”