nystagmus

Night Blindness, Congenital Stationary, CSNB1E

Clinical Characteristics
Ocular Features: 

Night blindness is a feature of many pigmentary and other retinal disorders, most of which are progressive.  However, there is also a group of genetically heterogeneous disorders, with generally stable scotopic defects and without RPE changes, known as congenital stationary night blindness (CSNB).  At least 10 mutant genes are responsible with phenotypes so similar that genotyping is usually necessary to distinguish them.  All are caused by defects in visual signal transduction within rod photoreceptors or defective photoreceptor-to-bipolar cell signaling with common ERG findings of reduced or absent b-waves and generally normal a-waves.  The photopic ERG is usually abnormal to some degree as well and visual acuity may be subnormal.  In the pregenomic era, subtleties of ERG responses were frequently used in an attempt to distinguish different forms of CSNB.  Genotyping now enables classification with unprecedented precision.

The onset of night blindness in type 1E occurs in early childhood and may be congenital.  Some degree of nystagmus is usually present.  It is usually only slowly progressive.

Systemic Features: 

No systemic disease is associated with congenital stationary night blindness.

Genetics

This type of congenital stationary night blindness is inherited in an autosomal recessive pattern resulting from homozygous or compound heterozygous mutations in GPR179.  The gene encodes an orphan G protein receptor.

Other autosomal recessive CSNB disorders are: CSNB2B (610427), CSNB1B (257270), and CSNB1C (613216).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment beyond correction of the refractive error is available but tinted lenses are sometimes used to enhance vision.

References
Article Title: 

Whole-Exome Sequencing Identifies Mutations in GPR179 Leading to Autosomal-Recessive Complete Congenital Stationary Night Blindness

Audo I, Bujakowska K, Orhan E, Poloschek CM, Defoort-Dhellemmes S, Drumare I, Kohl S, Luu TD, Lecompte O, Zrenner E, Lancelot ME, Antonio A, Germain A, Michiels C, Audier C, Letexier M, Saraiva JP, Leroy BP, Munier FL, Mohand-Sa?Od S, Lorenz B, Friedburg C, Preising M, Kellner U, Renner AB, Moskova-Doumanova V, Berger W, Wissinger B, Hamel CP, Schorderet DF, De Baere E, Sharon D, Banin E, Jacobson SG, Bonneau D, Zanlonghi X, Le Meur G, Casteels I, Koenekoop R, Long VW, Meire F, Prescott K, de Ravel T, Simmons I, Nguyen H, Dollfus H, Poch O, L?(c)veillard T, Nguyen-Ba-Charvet K, Sahel JA, Bhattacharya SS, Zeitz C. Whole-Exome Sequencing Identifies Mutations in GPR179 Leading to Autosomal-Recessive Complete Congenital Stationary Night Blindness. Am J Hum Genet. 2012 Feb 10;90(2):321-30.

PubMed ID: 
22325361

GPR179 Is Required for Depolarizing Bipolar Cell Function and Is Mutated in Autosomal-Recessive Complete Congenital Stationary Night Blindness

Peachey NS, Ray TA, Florijn R, Rowe LB, Sjoerdsma T, Contreras-Alcantara S, Baba K, Tosini G, Pozdeyev N, Iuvone PM, Bojang P Jr, Pearring JN, Simonsz HJ, van Genderen M, Birch DG, Traboulsi EI, Dorfman A, Lopez I, Ren H, Goldberg AF, Nishina PM, Lachapelle P, McCall MA, Koenekoop RK, Bergen AA, Kamermans M, Gregg RG. GPR179 Is Required for Depolarizing Bipolar Cell Function and Is Mutated in Autosomal-Recessive Complete Congenital Stationary Night Blindness. Am J Hum Genet. 2012 Feb 10;90(2):331-9.

PubMed ID: 
22325362

Microphthalmia, Isolated, with Cataract

Clinical Characteristics
Ocular Features: 

Isolated microphthalmia with cataract is clinically and genetically heterogeneous and remains to be fully delineated.  The cataracts occur congenitally.  Nystagmus was an additional feature in several individuals with MCOPCT2.  The basis for a third type of microphthalmia with cataract (MCOPCT3) is even less certain but microcornea was also present in several members of a single family.  Globe dimensions have not been reported, however, and the criterion for the diagnosis of microphthalmia in reported families is unknown.

Systemic Features: 

Several patients with MCOPCT1 have had mental retardation.

Genetics

Based on genetic data at least three entities may exist but they are discussed in this database as a group because so few families have been reported.  MCOPCT1 follows an autosomal dominant pattern and segregates with a single unknown mutation at 16p13.3.  Another family with a reciprocal translocation t(2;16)(p22.3;p13.3)  involving a breakpoint in the 16p13.3 region seems to support the idea that an altered gene in this location is responsible for the phenotype.  MCOPCT2 also usually follows an autosomal dominant pattern and seems to be caused by mutations in the SIX6 gene (14q23.1).  The mode of inheritance in MCOPCT3 is uncertain since the transmission pattern in one family suggested X-linked dominance while in another family only males were affected.  No mutation or locus has been identified.  

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Cataract surgery may be beneficial when vision is significantly compromised.

References
Article Title: 

Spinocerebellar Ataxia 1

Clinical Characteristics
Ocular Features: 

Early manifestations include gaze-evoked nystagmus and saccadic hypermetria.  Ophthalmoplegia develops later in the disease process.  Some patients experience a decrease in acuity and dyschromatopsia.  The ERG shows evidence of generalized rod and cone photoreceptor dysfunction in some patients.  Optic atrophy, central scotomas, central RPE changes, retinal arteriolar attenuation, and blepharospasm have also been reported.

Time-domain OCT has revealed microscopic changes in the macula with thinning of the inner-outer segment junction and nuclear layer in areas with RPE hypopigmentation. 

Systemic Features: 

This is a progressive cerebellar syndrome characterized by systems of ataxia, dysarthria, and bulbar palsy.  Speech is often scanning and explosive.  DTRs can be exaggerated, and dysmetria is common.  The mean age of onset is about age 40.  Some cognitive decline may occur.  Muscle atrophy, and symptoms of peripheral neuropathy can be present.  MRI shows atrophy in the cerebellum, spinal cord, and brainstem.  There is considerable variation in clinical expression.  Individuals with adult onset of symptoms can survive for 10-30 years whereas those with a juvenile-onset often do not live beyond the age of 16 years.

Genetics

This disorder is caused by an expanded CAG repeat in the ataxin-1 gene (ATXN1) at 6p23.  It is an autosomal dominant disorder.  Alleles with 39-44 or more CAG repeats are likely to be associated with symptoms. 

A male bias and the phenomenon of anticipation have been demonstrated in this disorder as in spinocerebellar ataxia 7 (SCA7) (164500), in which affected offspring of males with SCA develop disease earlier and symptoms progress more rapidly than in offspring of females.  This is often explained by the fact that males generally transmit a larger number of CAG repeats.

SCA7 (164500), also inherited in an autosomal dominant pattern and caused by expanded CAG repeats on chromosome 3, has many similar ocular and neurologic features.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Supportive care is often required.          

References
Article Title: 

Oculoauricular Syndrome

Clinical Characteristics
Ocular Features: 

This rare malformation syndrome affects primarily the eyes and ears.  The globes are small and usually have colobomas of both anterior and posterior segments.  The corneas likewise are small and often have opacities.  The anterior segment is dysplastic with anterior and/or posterior synechiae.  Glaucoma may be present.  The lenses may be small and often become cataractous.  There is a progressive rod-cone dystrophy associated with a pigmentary retinopathy.  Chorioretinal lacunae have been seen in the equatorial region.  The retinal degeneration is progressive, beginning with rod dysfunction but followed by deterioration of all receptors.  The onset in early childhood results in poor vision and nystagmus. 

Systemic Features: 

The external ears are abnormal.  The earlobes may have colobomas or may be aplastic.  The intertragic notch is often underdeveloped.  Audiograms and vestibular function tests, however, show normal function and MRI of the middle and inner ears likewise reveals no anatomic abnormalities.       

Among the few patients reported, dental anomalies, spina bifida oculta, and mild dyscrania have been noted in individual patients.

Genetics

This rare disorder has been reported in only a few families.  Based on parental consanguinity and homozygosity of mutations in the HMX1 gene (4p16.1) in affected sibs, this is an autosomal recessive disorder.  In one family there was a homozygous 26 bp deletion and in another a homozygous missense mutation.  The parents are heterozygous for the deletion.

HMX1 is a homeobox gene and the deletion abolishes its function by establishing a stop codon at position 112.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for the extraocular malformations.  Glaucoma treatment and cataract surgery should be considered although permanent visual rehabilitation is unlikely given the progressive nature of the rod-cone dystrophy.

References
Article Title: 

Cataracts, Congenital, Autosomal Recessive 3

Clinical Characteristics
Ocular Features: 

This type of congenital cataract has been reported in two unrelated Pakistani families.  The phenotype was dissimilar in the two families.  In one, only posterior subcapsular opacification was present.  In the other the cataract was membranous and accompanied by a corneal opacity, microcornea, and nystagmus.  Nothing is known about the course of the opacification.

Systemic Features: 

No systemic disease is apparently present.

Genetics

Consanguinity was reported for both families.  Fine mapping identified a locus at 1p34.3-p32.2 that cosegregates with the lens opacities but the mutation is unknown.  This region is distinct from the locus containing the mutation(s) causing Volkmann (115665) and posterior polar (116600) autosomal dominant cataracts.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Visually significant lens opacities could be removed.

References
Article Title: 

Nance-Horan Syndrome

Clinical Characteristics
Ocular Features: 

Congenital cataracts are a feature of this X-linked disorder.  These consist of bilateral, dense nuclear opacification (in most males) but sutural opacities are also seen, especially in carrier females.  If the nuclear cataracts are not treated promptly, severe amblyopia, nystagmus, and strabismus may result.  Microcornea, congenital glaucoma, scleral staphylomas, and retinal cystoid degeneration may also be present.  Microphthalmia has been described. These ocular signs are present in 90% of heterozygous females but they may be subtle and careful examination is required to identify them.  Cataract surgery is usually not required in females. 

Systemic Features: 

This is a developmental disorder in which facial dysmorphism and dental anomalies are consistent systemic features in affected males.  Some patients (30%) also have some intellectual impairment while others have developmental delays and behavior problems.  The pinnae may be anteverted and often appear large while the nose and nasal bridge are prominent.  The teeth in males are small and pointed or 'screwdriver shaped' and are widely separated (sometimes called Hutchinson teeth).  The enamel may be hypoplastic and dental agenesis can be present.  Supernumerary incisors have been described.  The facial and dental features may be present in female carriers but are less pronounced.  Females do not have intellectual impairment. 

Genetics

This is an X-linked recessive (dominant?) disorder resulting from mutations in the NHS gene located at Xp22.13.  However, heterozygous females may have clinical manifestations, including dense cataracts, and all offspring of such females need ophthalmological evaluations at birth.

It is likely that at least some cases of X-linked congenital cataract (CXN; 302200) represent this disorder because the facial dysmorphism may be subtle and easily missed in Nance-Horan.  Of course, the two disorders may also be allelic.  A variety of alterations in the NHS gene, including copy number variations, intragenic deletions, and duplication/triplication arrangements, have been found.  The occasionally subtle facial dysmorphology and the dental abnormalities are easily missed in patients in whom congenital cataracts are the primary clinical concern.  

Pedigree: 
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

Visually significant cataracts should be removed early to allow for normal visual maturation.  Glaucoma must be treated appropriately.  At risk males and females should have dental X-rays and dental surgery may be required.  Special education may be beneficial in males. 

References
Article Title: 

X-linked cataract and Nance-Horan syndrome are allelic disorders

Coccia M, Brooks SP, Webb TR, Christodoulou K, Wozniak IO, Murday V, Balicki M, Yee HA, Wangensteen T, Riise R, Saggar AK, Park SM, Kanuga N, Francis PJ, Maher ER, Moore AT, Russell-Eggitt IM, Hardcastle AJ. X-linked cataract and Nance-Horan syndrome are allelic disorders. Hum Mol Genet. 2009 Jul 15;18(14):2643-55.

PubMed ID: 
19414485

Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation

Burdon KP, McKay JD, Sale MM, Russell-Eggitt IM, Mackey DA, Wirth MG, Elder JE, Nicoll A, Clarke MP, FitzGerald LM, Stankovich JM, Shaw MA, Sharma S, Gajovic S, Gruss P, Ross S, Thomas P, Voss AK, Thomas T, Gecz J, Craig JE. Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation. Am J Hum Genet. 2003 Nov;73(5):1120-30.

PubMed ID: 
14564667

Nanophthalmos with Retinitis Pigmentosa

Clinical Characteristics
Ocular Features: 

Poor vision is present beginning in childhood and may progress to hand motion or even loss of light perception when retinal detachments occur.  Nystagmus has been seen in one patient.  Corneal diameters were 11 mm, the angles were open, and axial lengths were shortened to about 17 mm.  Alternating areas of hypo- and hyperfluorescence are seen with fluorescein angiography corresponding to areas with pigment clumping seen throughout the fundi.  The fundus pigmentation is atypical for retinitis pigmentosa, however, in spite of the title given by the authors.  No scotopic or photopic responses are seen on the ERG.  Drusen were present in the optic nerves. 

Systemic Features: 

No systemic disease is associated. 

Genetics

A single family with affected male and female sibs has been reported and a homozygous nonsense mutation in exon 5 of the CRB1 gene (1q31-32.1) was present in both. 

Another recessive form of microphthalmia with retinitis pigmentosa plus has been reported (611040) without nanophthalmos features and having a mutation in the MFRP gene. True nanophthalmos with retinopathy (267760) has some features similar to the disorder described here but with macular cysts.  No responsible mutation has been identified in this disorder however. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Low vision aids might be helpful in early stages of the disease. 

References
Article Title: 

Neuraminidase Deficiency

Clinical Characteristics
Ocular Features: 

A cherry red spot is may be seen in late childhood or early adolescence.  It occurs in nearly 100% of patients with type I while only 75% of type II patients have this feature possibly because their early death from the more severe systemic disease prevents full ascertainment.  Visual acuity is reduced, sometimes severely.  Some but not all individuals have corneal and lens opacities.  A subtle corneal haze has also been seen.  Nystagmus has been reported. 

Systemic Features: 

This is a neurodegenerative disorder with progressive deterioration of muscle and central nervous system functions.  Myoclonus, mental deterioration, hepatosplenomegaly, muscle weakness and atrophy are common.  The defect in neuraminidase activity leads to abnormal amounts of sialyl-oligosaccharides in the urine.  Spinal deformities such as kyphosis are common.  Deep tendon reflexes are exaggerated.  Ataxia and hearing loss may be present.  Coarse facies, a barrel chest, and short stature are characteristic.  Hepatic cells contain numerous vacuoles and numerous inclusions.

Sialidosis types I and II are both caused by mutations in the neuroaminidase gene.  Type I is associated with milder disease than type II which has an earlier age of onset and may present in infancy or even begin in utero.  Early death within two years of age is common in the congenital or infantile forms.  There is, however, significant variability in age of onset and the course of disease among types. 

Genetics

The sialidoses are autosomal recessive lysosomal storage disorders resulting from mutations in the NEU1 gene (6p21.3) which lead to an intracellular accumulation of glycoproteins containing sialic acid residues.  Both types I and II are caused by mutations in the same gene. 

Treatment
Treatment Options: 

Treatment is focused on symptom management. 

References
Article Title: 

Neurodegeneration with Brain Iron Accumulation

Clinical Characteristics
Ocular Features: 

Optic atrophy is a major ocular feature and the primary cause of visual impairment.  A minority (25%) of patients also have a diffuse fleck retinopathy with a bull’s eye maculopathy.  Later the retinopathy may resemble retinitis pigmentosa with a bone spicule pattern. Nystagmus is often present.  These signs usually follow systemic signs such as difficulties in locomotion.  An apraxia of eyelid opening has been noted and some patients have blepharospasm. 

Systemic Features: 

This is a progressive disorder of the basal ganglia with prominent symptoms of extrapyramidal dysfunction.  Onset is in early childhood or in the neonatal period with delayed development and sometimes mental retardation.  Choreoathetoid writhing movements, stuttering, dysphagia, muscle rigidity, and intermittent dystonia are prominent features.  Seizures are uncommon.  Older individuals may exhibit dementia and ambulation is eventually impaired.  The MRI usually shows an area of hyperintensity in the medial globus pallidus that has been called the ‘eye of the tiger’ sign but this is not pathognomonic.  Axonal degeneration with accumulation of spheroidal inclusions can be seen histologically. 

Genetics

The title of this disorder ‘neurodegeneration with brain iron accumulation’ actually refers to a group of disorders with somewhat common characteristics.  Pentothenate kinase-associated neurodegeneration or NB1A1 (234200) is  the most common of these. 

Types  NBIA2A (256600) and NBIA2B (610217) are caused by mutations in the PLA2G6 gene (22q13.1).  The former can be seen neonatally but usually has its onset in the first two years of life and is sometimes called infantile neuroaxonal dystrophy or Seitelberger disease.  Death may occur before the age of 10 years.  Signs of motor neuron and cerebellar disease are more prominent than in NB1A1. 

NBIA2B has a later onset (4-5 years) and profound sensorimotor impairment but there are many overlapping features and the nosology is confusing.  Mutations in the FTL gene cause yet another form designated NBIA3 (606159) but ocular signs seem to be absent. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is evidence that treatment with deferiprone reduces the amount of iron accumulation in the globus pallidus with motor improvement in at least some patients.  Most patients require supportive care.

References
Article Title: 

Albinism, Oculocutaneous, Type III

Clinical Characteristics
Ocular Features: 

The irides may be multicolored with the central potion light brown and the peripheral areas blue-gray.  Translucency of a punctate and radial nature is present.  Nystagmus is present in almost all cases and strabismus is present in nearly half.  Visual acuity is in the range of 20/60 to 20/200.   Photophobia is less severe than in other types of oculocutaneous albinism, possibly because the vast majority of individuals (86%) have some pigmentation in the fundus. 

Systemic Features: 

The hair in dark-skinned people may be medium brown while the skin is often light brown and subject to faint tanning.  However, the hair is often copper-red in color which has given rise to the designation rufous oculocutaneous albinism. 

Genetics

This tyrosinase-positive type of albinism is sometimes called 'rufous' (ROCA) or 'brown' (BOCA) oculocutaneous albinism and is frequently found in dark-skinned individual such as Africans, African-Americans, and Hispanics.  Like other types it is inherited in an autosomal recessive pattern.  Mutations in the tyrosinase-related protein-1, TYRP1 (9p23), are responsible which seems to lead to an arrest in melanin maturation and a decrease in the amount of insoluble melanin in melanocytes.

Other autosomal recessive types of oculocutaneous albinism are: OCA1 (203100, 606952), OCA2 (203200), and OCA4 (606574). 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for the hypopigmentation.  However, precautions against excessive sun exposure are advised.  Low vision aids can be helpful. 

References
Article Title: 

Oculocutaneous albinism

Gronskov K, Ek J, Brondum-Nielsen K. Oculocutaneous albinism. Orphanet J Rare Dis. 2007 Nov 2;2:43. Review.

PubMed ID: 
17980020

Pages

Subscribe to RSS - nystagmus