Deafness and Myopia Syndrome
Jessica L Ordonez, MS, CGC and Mustafa Tekin, MD.
Author Information and AffiliationsInitial Posting: January 15, 2015; Last Update: September 14, 2017.
Estimated reading time: 12 minutes
Summary
Clinical characteristics.
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.
Management.
Treatment of manifestations: For hearing loss: use of hearing habilitation devices including hearing aids and vibrotactile hearing tools; cochlear implantation may be considered in individuals with severe-to-profound sensorineural hearing loss and auditory neuropathy spectrum disorder; enrollment in appropriate early-intervention and educational programs for the hearing impaired. For myopia: 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.
Agents/circumstances to avoid: Known environmental factors for hearing loss (e.g., loud noises) and ototoxic medications.
Evaluation of relatives at risk: If the SLITRK6 pathogenic variants in the family are known, molecular genetic testing can be used to clarify the genetic status of at-risk sibs. If a molecular diagnosis has not been established, clinical audiology and ophthalmology evaluations should be considered for at-risk sibs.
Genetic counseling.
DFNMYP syndrome is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for a pregnancy at increased risk are possible if the SLITRK6 pathogenic variants have been identified in an affected family member.
Diagnosis
Suggestive Findings
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
Establishing the Diagnosis
No formal clinical diagnostic criteria have been established for DFNMYP syndrome.
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 (see Table 1) confirms the diagnosis.
Molecular genetic testing approaches can include single-gene testing, use of a multigene panel, and more comprehensive genomic testing:
Single-gene testing. Sequence analysis of
SLITRK6 is performed first. Gene-targeted
deletion/duplication analysis can be considered if only one or no
pathogenic variant is found. However, to date, no large
SLITRK6 deletions or duplications have been reported.
A multigene panel that includes
SLITRK6 and other genes of interest (see
Differential Diagnosis) may be considered. Note: (1) The genes included in the panel and the diagnostic
sensitivity of the testing used for each
gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this
GeneReview; thus, clinicians need to determine which multigene panel is most likely to identify the genetic cause of the condition at the most reasonable cost while limiting identification of variants of
uncertain significance and pathogenic variants in genes that do not explain the underlying
phenotype. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused
exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include
sequence analysis,
deletion/duplication analysis, and/or other non-sequencing-based tests.
For an introduction to multigene panels click
here. More detailed information for clinicians ordering genetic tests can be found
here.
More comprehensive genomic testing (when available) including
exome sequencing, mitochondrial sequencing, and
genome sequencing may be considered. Such testing may provide or suggest a diagnosis not previously considered (e.g., mutation of a different
gene or genes that results in a similar clinical presentation).
For an introduction to comprehensive
genomic testing click
here. More detailed information for clinicians ordering genomic testing can be found
here.
Table 1.
Molecular Genetic Testing Used in Deafness and Myopia Syndrome
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| Gene 1 | Method | Proportion of Probands with Pathogenic Variants 2 Detectable by Method |
|---|
|
SLITRK6
| Sequence analysis 3 | 4/4 4 |
| Gene-targeted deletion/duplication analysis 5 | None reported 6 |
- 1.
- 2.
- 3.
- 4.
- 5.
Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.
- 6.
Clinical Characteristics
Clinical Description
Deafness and myopia (DFNMYP) syndrome was described by Tekin et al [2013] in nine individuals with only deafness and myopia from three families, of Turkish, Greek, and Amish ancestry; all nine were found to be homozygous for SLITRK6 pathogenic variants.
Sensorineural hearing loss (SNHL) was bilateral in all affected individuals, congenital in one and prelingual in 8/9. SNHL was progressive and required hearing aids in all. Severity of hearing loss ranged from moderate (2/9) to severe (5/9) to profound (2/9).
Sensorineural hearing loss progressed from moderate to profound by early adulthood in nine additional affected individuals from an endogamous Amish population [Morlet et al 2014]. An auditory neuropathy-spectrum disorder characterized by absent middle-ear muscle reflexes (MEMRs) and otoacoustic emissions (OAEs), large and prolonged cochlear microphonics (CMs), desynchronized auditory brain stem responses (ABRs), and progressive pure tone hearing loss was described [Morlet et al 2014].
Affected individuals had normal gross motor development. None had balance problems, vertigo, or dizziness. Vestibular testing and temporal bone CT were normal in one affected individual from each family.
Myopia was diagnosed in infancy or early childhood in seven individuals on whom data were available. Myopia was severe in all seven individuals (range: -6 to -11 diopters) and required corrective lenses. Although no details of myopia treatment or complications were available, none of the potential complications of high myopia was observed in any of the reported individuals at the time of reporting.
Life span does not appear to be altered in individuals with DFNMYP syndrome; however, the oldest individuals with a molecularly confirmed diagnosis are only in their late 30s.
Genotype-Phenotype Correlations
All reported individuals to date with DFNMYP syndrome have homozygous nonsense SLITRK6 variants. No significant differences in clinical phenotype have been associated with specific genotypes.
Prevalence
Due to the rarity of the syndrome, no prevalence estimates have been established.
Differential Diagnosis
See Hereditary Deafness and Hearing Loss Overview.
Disorders with deafness and myopia to specifically consider include the following:
Stickler syndrome, a clinically variable connective tissue disorder characterized by ocular, auditory, skeletal, and orofacial anomalies. Ocular findings typically include high myopia with cataracts and retinal detachment. Hearing loss is conductive and sensorineural. Severity of hearing loss is variable and may be progressive. Stickler syndrome, caused by mutation of
COL2A1,
COL11A1, or
COL11A2, is inherited in an
autosomal dominant manner; Stickler syndrome caused by mutation of
COL9A1,
COL9A2, or
COL9A3 is inherited in an
autosomal recessive manner. Although myopia and sensorineural hearing loss are part of DFNMYP syndrome, individuals with DFNMYP syndrome do not manifest the skeletal and craniofacial findings traditionally seen in individuals with Stickler syndrome.
Donnai-Barrow syndrome
(DBS), a multiple
congenital anomaly syndrome characterized by typical craniofacial features, ocular findings, sensorineural hearing loss, brain anomalies, intellectual disability, and congenital diaphragmatic hernia and/or omphalocele. High myopia is typically accompanied by retinal detachment, progressive vision loss, and iris coloboma. Hearing loss may be progressive and variable in severity. The constellation of craniofacial findings typically includes marked ocular hypertelorism, large anterior fontanelle, wide metopic suture, widow’s peak in anterior hairline, depressed nasal bridge, short nose, and posteriorly rotated ears. DBS can be caused by mutation of
LRP2 and is inherited in an
autosomal recessive manner. In contrast to individuals with DFNMYP syndrome, individuals with DBS have multiple congenital anomalies and craniofacial and neurologic findings in addition to myopia and hearing loss.
Management
Evaluations Following Initial Diagnosis
To establish the extent of disease and needs in an individual diagnosed with deafness and myopia (DFNMYP) syndrome, the following evaluations are recommended if they have not already been completed:
Audiology evaluation for sensorineural hearing loss and auditory neuropathy spectrum disorder
Ophthalmology evaluation for myopia and other ocular comorbidities
Evaluation by early intervention/educational programs for the hearing impaired including baseline speech and language assessment in children
Consultation with a clinical geneticist and/or genetic counselor
Treatment of Manifestations
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 [
Breneman et al 2012].
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
The following are appropriate:
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 including cataracts, glaucoma, and retinal detachment
Yearly evaluations by a clinical geneticist familiar with hereditary forms of deafness
Agents/Circumstances to Avoid
Individuals with hearing loss should avoid the following:
Evaluation of Relatives at Risk
It is appropriate to evaluate older and younger sibs of a proband in order to identify as early as possible those who would benefit from prompt treatment of hearing loss and myopia. Evaluations can include:
See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.
Therapies Under Investigation
Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.
Genetic Counseling
Genetic counseling is the process of providing individuals and families with
information on the nature, mode(s) of inheritance, and implications of genetic disorders to help them
make informed medical and personal decisions. The following section deals with genetic
risk assessment and the use of family history and genetic testing to clarify genetic
status for family members; it is not meant to address all personal, cultural, or
ethical issues that may arise or to substitute for consultation with a genetics
professional. —ED.
Mode of Inheritance
Deafness and myopia (DFNMYP) syndrome is inherited in an autosomal recessive manner.
Risk to Family Members
Parents of a proband
The parents of an affected child are obligate heterozygotes (i.e., carriers of one
SLITRK6 pathogenic variant).
Although low myopia (<-3 diopters) of early and adult onset has been reported among some
carrier parents,
SLITRK6 heterozygotes are not at risk of developing hearing loss or the high myopia characteristic of DFNMYP syndrome.
Sibs of a proband
Offspring of a proband. The offspring of an individual with DFNMYP syndrome are obligate heterozygotes (carriers) for a pathogenic variant in SLITRK6.
Other family members. Each sib of the proband’s parents is at a 50% risk of being a carrier of a SLITRK6 pathogenic variant.
Carrier Detection
Carrier testing for at-risk relatives requires prior identification of the SLITRK6 pathogenic variants in the family.
Prenatal Testing and Preimplantation Genetic Testing
Once the SLITRK6 pathogenic variants have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.
Differences in perspective may exist among medical professionals and within families regarding the use of prenatal testing. While most centers would consider use of prenatal testing to be a personal decision, discussion of these issues may be helpful.
Resources
GeneReviews staff has selected the following disease-specific and/or umbrella
support organizations and/or registries for the benefit of individuals with this disorder
and their families. GeneReviews is not responsible for the information provided by other
organizations. For information on selection criteria, click here.
Alexander Graham Bell Association for the Deaf and Hard of Hearing
Phone: 866-337-5220 (toll-free); 202-337-5221 (TTY)
Fax: 202-337-8314
Email: info@agbell.org
American Society for Deaf Children
Phone: 800-942-2732 (ASDC)
Email: info@deafchildren.org
BabyHearing.org
This site, developed with support from the National Institute on Deafness and Other Communication Disorders, provides information about newborn hearing screening and hearing loss.
National Association of the Deaf
Phone: 301-587-1788 (Purple/ZVRS); 301-328-1443 (Sorenson); 301-338-6380 (Convo)
Fax: 301-587-1791
Email: nad.info@nad.org
National Institute on Deafness and Other Communication Disorders (NIDCD)
31 Center Drive
MSC 2320
Bethesda MD 20892-2320
Molecular Genetics
Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.
Table A.
Deafness and Myopia Syndrome: Genes and Databases
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Data are compiled from the following standard references: gene from
HGNC;
chromosome locus from
OMIM;
protein from UniProt.
For a description of databases (Locus Specific, HGMD, ClinVar) to which links are provided, click
here.
Gene structure.
SLITRK6 contains two exons; exon 1 is noncoding. The full-length transcript spans 6.6 kb (6,562 bp) of genomic DNA. The cDNA NM_032229.2 comprises 4199 bp encoding 841 amino acids. For a detailed summary of gene and protein information, see Table A, Gene.
Pathogenic variants. Three SLITRK6 pathogenic variants, all nonsense, have been described in DFNMYP syndrome. The c.1240C>T variant has been observed more than once among the Amish.
Table 2.
SLITRK6 Pathogenic Variants Discussed in This GeneReview
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| DNA Nucleotide Change | Predicted Protein Change | Reference Sequences |
|---|
| c.541C>T | p.Arg181Ter |
NM_032229.2
NP_115605.2
|
| c.890C>A | p.Ser297Ter |
| c.1240C>T | p.Gln414Ter |
Variants listed in the table have been provided by the authors. GeneReviews staff have not independently verified the classification of variants.
GeneReviews follows the standard naming conventions of the Human Genome Variation Society (varnomen.hgvs.org). See Quick Reference for an explanation of nomenclature.
Normal gene product. The SLITRK family of genes encodes six neuronal transmembrane proteins ‒ mainly found in neural tissue ‒ that modulate neurite outgrowth and synaptic development [Aruga 2003, Aruga & Mikoshiba 2003, Takahashi et al 2012].
SLITRK6 has an extracellular N-terminal domain that contains two leucine-rich domains highly homologous to SLIT domains; it also has a transmembrane domain and an intracellular C-terminus with two conserved tyrosine phosphorylation sites homologous to receptor sites from the NTRK-neurotrophin family. The expression of SLITRK6 in the inner ear promotes innervation and survival of sensory neurons.
Unlike other members of the SLITRK family, which are broadly expressed in developing mouse brain, SLITRK6 is differentially expressed in the auditory system during embryonic and postnatal life; expression is strongest in the inner ear, and modest in the thalamus and lateral geniculate nucleus [Beaubien & Cloutier 2009, Katayama et al 2009].
Abnormal gene product. The reported pathogenic variants (which impair cell surface expression and synapse-inducing activity of SLITRK6) did not trigger nonsense-mediated mRNA decay, produced truncated products, and are predicted to result in loss of function. However, the possibility of a toxic gain-of-function mechanism from misdirection to the intracellular space from loss of an intracellular C-terminal domain cannot be excluded [Morlet et al 2014].
Cancer and Benign Tumors
Copy number changes were analyzed from human papillary thyroid cancerous tumors (PTC) using array CGH [Heiliger et al 2012]. SLITRK6 deletions were detected in 16% of PTC samples compared to normal tissue. Deletions were not detected in PTC samples from a transgenic mouse model for thyroid neoplasia.
References
Literature Cited
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Breneman AI, Gifford RH, Dejong MD. Cochlear implantation in children with auditory neuropathy spectrum disorder: long-term outcomes.
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Chapter Notes
Acknowledgments
This work was supported by an NIH/NIDCD grant R01DC009645 to MT.
Revision History
14 September 2017 (sw) Comprehensive update posted live
15 January 2015 (me) Review posted live
8 September 2015 (jo) Original submission
