neurosensory hearing loss

Usher Syndrome Type IV

Clinical Characteristics
Ocular Features: 

Nyctalopia is a complaint in adults in by midlife but most individuals deny visual symptoms prior to the 5th decade.  Perimetry reveals a ring-shaped scotoma extending from the paracentral area to the midperiphery (5 to 30 degrees).  Full-field ERGs show decreased photoreceptor responses by the 5th decade or late with the rods more severely affected than the cones.  Some dyschromatopsia is usually present.  Patients have a significant and progressive loss of visual acuity.  Ring-shaped areas of retinal pigment atrophy may extend from the pericentral area to the temporal arcades with relative sparing of the fovea early but older individuals have foveal degeneration as well.  The Arden EOG ratio is usually lower than normal.

Systemic Features: 

Five individuals in three Yemenite Jewish families have been described with this type of Usher syndrome.  A neurosensory hearing loss is present by midlife but no other systemic signs have been reported. 

Genetics

Homozygosity of a missense mutation in the ARSG gene (17q24.2) is responsible for this condition.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No specific treatment for this condition is available.  However, assistive hearing devices such as cochlear implants and corrective lenses with appropriate tinting can be beneficial.

References
Article Title: 

Retinal Dystrophy With Or Without Extraocular Anomalies

Clinical Characteristics
Ocular Features: 

Progressive deterioration of rod and cone function is characteristic of this condition which is clinically manifest as some variation of pigmentary retinopathy.  Early (second decade) pigmentary changes resemble retinitis pigmentosa but in the fourth and fifth decades they resemble a peripheral pattern-like reticular dystrophy.  Central chorioretinal atrophy has been described in some patients.  The ERG responses are abnormal suggesting loss of the photoreceptors.

Systemic Features: 

Extraocular anomalies are highly variable ranging from a mild intellectual disability in some patients, to thyroid goiter and nodules, and primary ovarian insufficiency.  Sensorineural hearing loss was present in one family and one patient had pulmonary fibrosis.

Genetics

Homozygous missense mutations in the RCBTB1 gene (13q14) seem to be responsible for this condition.  Six families have been reported.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Isolated and Syndromic Retinal Dystrophy Caused by Biallelic Mutations in RCBTB1, a Gene Implicated in Ubiquitination

Coppieters F, Ascari G, Dannhausen K, Nikopoulos K, Peelman F, Karlstetter M, Xu M, Brachet C, Meunier I, Tsilimbaris MK, Tsika C, Blazaki SV, Vergult S, Farinelli P, Van Laethem T, Bauwens M, De Bruyne M, Chen R, Langmann T, Sui R, Meire F, Rivolta C, Hamel CP, Leroy BP, De Baere E. Isolated and Syndromic Retinal Dystrophy Caused by Biallelic Mutations in RCBTB1, a Gene Implicated in Ubiquitination. Am J Hum Genet. 2016 Aug 4;99(2):470-80.

PubMed ID: 
27486781

Cataracts, Congenital, Deafness, Short Stature, Developmental Delay

Clinical Characteristics
Ocular Features: 

The facial features superficially resemble those often seen in Down syndrome patients with slanting (up or down) lid fissures and epicanthal folds. The amount of ptosis is variable.  Lens opacities are usually congenital in origin.  Hypopigmentation of the macula has been noted in two individuals.

Systemic Features: 

The characteristic facies may be evident at birth and requires karyotyping to rule out the trisomy of Down syndrome. Brachycephaly and a flat face may be present.  The mouth is often small and the nasal tip is shortened while the philtrum is long and smooth.  Some degree of intellectual disability and neurosensory hearing loss soon become evident.  There is postnatal growth delay and most individuals are short in stature.  The ears are low-set and rotated posteriorly.

The skeletal anomalies are not fully delineated but one patient had bilateral radioulnar synostosis while hip chondrolysis requiring hip replacement has been seen in two adult individuals.  Limited motion may be present in some joints, both large and small.  Seizures have been reported in a few individuals. Nails may appear dystrophic and there are variable tooth anomalies present. 

Genetics

The responsible heterozygous mutations are in the MAF gene (16q22-q23).  Type 4 (CCA4) (610202) autosomal dominant cerulean cataracts with multiple morphologies may also result from mutations in this transcription factor gene.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No general treatment for this condition is known.  Congenital cataracts can be removed.  Some patients may benefit from special education.   Seizure medications may be indicated and some patients can benefit from hearing aids.  Severe joint disease may require replacement.

References
Article Title: 

Mutations Impairing GSK3-Mediated MAF Phosphorylation Cause Cataract, Deafness, Intellectual Disability, Seizures, and a Down Syndrome-like Facies

Niceta M, Stellacci E, Gripp KW, Zampino G, Kousi M, Anselmi M, Traversa A, Ciolfi A, Stabley D, Bruselles A, Caputo V, Cecchetti S, Prudente S, Fiorenza MT, Boitani C, Philip N, Niyazov D, Leoni C, Nakane T, Keppler-Noreuil K, Braddock SR, Gillessen-Kaesbach G, Palleschi A, Campeau PM, Lee BH, Pouponnot C, Stella L, Bocchinfuso G, Katsanis N, Sol-Church K, Tartaglia M. Mutations Impairing GSK3-Mediated MAF Phosphorylation Cause Cataract, Deafness, Intellectual Disability, Seizures, and a Down Syndrome-like Facies. Am J Hum Genet. 2015 May 7;96(5):816-25.

PubMed ID: 
25865493

Perrault Syndrome

Clinical Characteristics
Ocular Features: 

Nystagmus and limited extraocular movements are usually present in PRLTS1.  Optic atrophy and poor visual acuity have been reported. Ptosis may be present.  The clinical manifestations are variable among and within the types.  Rod dysfunction and ‘retinal atrophy’ were reported in one patient.  The majority of patients have had only limited ocular evaluations.

Systemic Features: 

This is a sex-influenced condition in which both sexes have a sensorineural hearing deficit and neurodegenerative disease (both central and peripheral) but only the females have gonadal dysgenesis.  Motor development is often delayed and ataxia along with a peripheral sensory neuropathy and a variable degree of limb weakness can be present.  Learning difficulties, cognitive decline, and frank mental retardation are frequently described.  The cerebellum may be atrophic.

There is considerable variability in the clinical signs.

Genetics

The combination of hearing loss in males and females, ovarian dysgenesis in females, and variable neurologic signs including external ophthalmoplegia and sometimes optic atrophy is known as Perrault syndrome.  The ocular movement abnormalities are seen primarily in PRLTS1. 

At least 5 unique mutations have been found accounting for types PRLTS1-5.  PRLTS1 (233400) results from mutations in HSD17B4 (5q23.1), type PRLTS2 (614926) is caused by mutations in the HARS2 gene, PPRLTS3 (614129) by mutations in the CLPP gene, PRLTS4 (615300) by mutations in the LARS2 gene, and PRLTS5 (616138) by mutations in C10orf2 (listed in this database as External Ophthalmoplegia, C10orf2, and mtDNA mutations,.

The inheritance pattern among different types may be autosomal recessive or autosomal dominant.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is known.

References
Article Title: 

Perrault syndrome: further evidence for genetic heterogeneity

Jenkinson EM, Clayton-Smith J, Mehta S, Bennett C, Reardon W, Green A, Pearce SH, De Michele G, Conway GS, Cilliers D, Moreton N, Davis JR, Trump D, Newman WG. Perrault syndrome: further evidence for genetic heterogeneity. J Neurol. 2012 May;259(5):974-6.

PubMed ID: 
22037954

Perrault syndrome in sisters

McCarthy DJ, Opitz JM. Perrault syndrome in sisters. Am J Med Genet. 1985 Nov;22(3):629-31.

PubMed ID: 
4061497
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