Deafness and myopia syndrome

Other Names: High myopia-sensorineural deafness syndrome Deafness and myopia syndrome is rare condition that affects both hearing and vision. Beginning at birth or in early infancy, people with this condition have moderate to profound hearing loss in both ears that generally becomes worse over time. Affected people also develop severe myopia (nearsightedness) later in infancy or early childhood.

Epidemiology

The prevalence of deafness and myopia syndrome is unknown. Only a few affected families have been described in the medical literature.

Cause

Deafness and myopia syndrome is caused by mutations in the SLITRK6 gene. The protein produced from this gene is found primarily in the inner ear and the eye. This protein promotes growth and survival of nerve cells (neurons) in the inner ear that transmit auditory signals. It also controls (regulates) the growth of the eye after birth. In particular, the SLITRK6 protein influences the length of the eyeball (axial length), which affects whether a person will be nearsighted or farsighted, or will have normal vision. The SLITRK6 protein spans the cell membrane, where it is anchored in the proper position to perform its function.

SLITRK6 gene mutations that cause deafness and myopia syndrome result in an abnormally short SLITRK6 protein that is not anchored properly to the cell membrane. As a result, the protein is unable to function normally. Impaired SLITRK6 protein function leads to abnormal nerve development in the inner ear and improperly controlled eyeball growth, resulting in the hearing loss and nearsightedness that occur in deafness and myopia syndrome.

Inheritance

Autosomal recessive inheritance, a 25% chance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

Deafness and myopia (DFNMYP) syndrome is characterized by bilateral, congenital or prelingual deafness (sensorineural hearing loss or auditory neuropathy spectrum disorder) and high myopia (>-6 diopters). In individuals with a molecularly confirmed diagnosis reported to date, hearing loss was progressive and severity ranged from moderate to profound. Vestibular testing was normal. Myopia was diagnosed at infancy or early childhood.

Diagnosis

Deafness and myopia (DFNMYP) syndrome should be suspected in individuals with the following:

• Moderate-to-profound, bilateral, congenital or prelingual sensorineural hearing loss or auditory neuropathy spectrum disorder (sensorineural hearing loss originates from problems in the inner ear or the auditory nerve). Auditory neuropathy spectrum disorder is characterized by normal outer hair cell function (present otoacoustic emissions [OAE] and/or cochlear microphonic), suggesting that the hearing loss results from abnormal inner hair cells, synapses, or auditory nerve function that can be demonstrated with an absent or abnormal auditory brain stem response (ABR) test.
• High myopia (g>-6 diopters)
• Nondysmorphic facial appearance and normal temporal bone structure
• No neurologic, connective tissue, or other ocular manifestations

The diagnosis of DFNMYP is established in a proband with the above suggestive findings; identification of biallelic pathogenic variants in SLITRK6 on molecular genetic testing confirms the diagnosis.

Treatment

Appropriate treatment includes the following:

• Implementation of hearing habilitation devices including hearing aids and vibrotactile hearing tools as needed
• Consideration of cochlear implantation (CI) in individuals with severe-to-profound sensorineural hearing loss and auditory neuropathy spectrum disorder. Although no CI has been reported among individuals with deafness and myopia syndrome, favorable outcome of CI has been reported in children with auditory neuropathy spectrum disorder .
• Enrollment in early intervention programs and educational programs for the hearing impaired to maximize long-term speech and language outcomes
• Routine correction of refractive error

Surveillance: ENT and audiology evaluations at least yearly; regular speech and language evaluation to monitor language development; regular ophthalmology evaluations to monitor for potential complications from high myopia; yearly evaluations by a clinical geneticist familiar with hereditary forms of deafness.

NIH genetic and rare disease info

• NIH info on Deafness and myopia syndrome

Deafness and myopia syndrome is a rare disease.

Deafness and myopia syndrome Resources
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