esotropia

Familial Acorea, Microphthalmia and Cataract Syndrome

Clinical Characteristics
Ocular Features: 

The pupil is obscured or absent secondary to fibrous overgrowth.  Microcornea and microphthalmia are present.  Iridocorneal adhesions are commonly seen on ultrasonic examination and anterior chamber angles may be narrow.  The corneas are clear but thickened centrally.  Nystagmus and esotropia have been reported.

The iris is rudimentary with a poorly developed stromal pattern and sometimes eccentrically located holes.  The ultrasound may reveal remnants of degenerative lens capsules.  Axial length in infants has been measured at about 14.7 mm but increases to 17 mm in children.  In adults the axial length is about 20 mm.  Refractive errors of +20-21 diopters have been measured.  Visual acuity is poor from birth but can be improved to some extent following pupiloplasty and lens extraction.  Intraocular pressure can be normal but one patient developed an increase in the 4th decade of life.  OCT and direct visualization of the fundus in several cases revealed normal retinal architecture and anatomy.

Systemic Features: 

None reported.  Specialty examinations failed to find any hearing loss or neurological deficits.

Genetics

The single 4 generation family tree reported is consistent with autosomal dominant inheritance.  Several likely loci on chromosomes 1, 5, 8, 11, and 17 have been reported but no candidate gene has been identified. 

Other conditions in which small pupils are found are Pierson syndrome (609049) and Warburg micro syndrome (600118) but these are associated with significant systemic abnormalities.  

Congenital microcoria (156600) is an autosomal dominant disorder with mild axial myopia and goniodysgenesis resulting from an unidentified mutation on chromosome 13.  Glaucoma is a common finding as is some iris hypoplasia.  Despite some clinical similarities, this is likely a unique disorder.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Some improvement in visual acuity has been reported following lensectomy and reconstruction of the pupil.

References
Article Title: 

Congenital Disorder of Glycosylation, Type Ia

Clinical Characteristics
Ocular Features: 

Strabismus, roving eye movements (and nystagmus), and visual inattention are found in nearly all patients. Esotropia with defective abduction seems to be the most common oculomotor finding and may be present at birth.  Cataracts, ocular colobomas, oculomotor apraxia, disc pallor, and glaucoma have also been reported.  Vision is always subnormal. Reports of ocular disease before modern genotyping are not specific to the subtypes of CDG I now recognized.

This is a congenital, progressive disorder of photoreceptor degeneration with a later onset of progressive pigmentary retinopathy.  It is described in some cases as a typical retinitis pigmentosa.  The ERG is abnormal in all patients even if the pigmentary pattern is atypical for RP.  Rod responses are usually absent while the cone b-wave implicit time is delayed.  The degree of photoreceptor damage is variable, however.  Extended retinal function among younger patients suggest that the ‘on-pathway’ evolving synapses in the outer plexiform layer among photoreceptors, bipolar cells, and horizontal cells is severely dysfunctional.

Systemic Features: 

This is a multisystem disorder, often diagnosed in the neonatal period by the presence of severe encephalopathy with hypotonia, hyporeflexia, and poor feeding.  Failure to thrive, marked psychomotor retardation, delayed development, growth retardation, and ataxia become evident later in those who survive.  Cerebellar and brainstem atrophy with a peripheral neuropathy can be demonstrated during late childhood.  Some older patients have a milder disease, often with muscle atrophy and skeletal deformities such as kyphoscoliosis and a fusiform appearance of the digits.  Maldistribution of subcutaneous tissue is often seen resulting in some dysmorphism, especially of the face.  Hypogonadism and enlargement of the labia majora are commonly present.  Some patients have evidence of hepatic and cardiac dysfunction which together with severe infections are responsible for a 20% mortality rate in the first year of life.

Genetics

This is one of a group of genetically (and clinically) heterogeneous autosomal recessive conditions caused by gene mutations that result in enzymatic defects in the synthesis and processing of oligosaccharides onto glycoproteins. This type (Ia) is the most common.   The mutation lies in the PMM2 gene (16p13.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Most children require tube feeding with nutritional supplements.  The risk of systemic infections is high.  Those patients who survive into the second decade and beyond may require orthopedic procedures and are confined to wheelchairs.  Physical, occupational, and speech therapy along with parental support are important.

References
Article Title: 

Macular Dystrophy, Vitelliform 2

Clinical Characteristics
Ocular Features: 

Best disease primarily affects the macular and paramacular areas.  The classical lesion resembles an egg yolk centered on the fovea.  Most patients, however, never exhibit the typical vitelliform lesion and may instead have normal maculae, or irregular yellowish deposits that may even be extrafoveal.  Histologically the RPE contains increased amounts of lipofuscin.  The ‘egg yolk’ is located beneath the neurosensory retina and the overlying retinal circulation often remains intact.  It can evolve into a ‘scrambled egg’ appearance and an apparent fluid level may be evident.  Some patients exhibit only RPE changes including hyper-  or hypopigmentation throughout the macula.  Choroidal neovasculariztion with hemorrhage leading to scarring and gliosis are uncommon but present a serious risk to vision.  The common end point for symptomatic patients is some degree of photoreceptor damage.

Until recently, most reports of Best macular dystrophy did not include genotypic data.  It is therefore difficult to classify families with variants of the disease, such as adult-onset or atypical vitelliform dystrophy but these at least suggest that this may be a heterogeneous disorder.  At the present time, the diagnosis should be reserved for those with an abnormal light-to-dark (Arden) ratio on electro-oculography and a mutation in the BEST1 gene. 

Visual function varies widely and has considerable fluctuation.   As many as 7-9 percent of patients are asymptomatic throughout life and few have vision loss to 20/200.  Many individuals maintain vision of 20/40 or better throughout life.  Some experience episodic acute vision loss to 20/80 or worse but often recover to at least 20/30.  It has been reported that as many as 76 per cent under the age of 40 retain 20/40 and 30 per cent retain this level of vision into the 5th and 6th decade of life.

Other ocular manifestations include hyperopia, esotropia, and, rarely, shallow anterior chambers with angle closure glaucoma.

Systemic Features: 

None have been reported.

Genetics

A mutation in the bestrophin gene (BEST1) located on chromosome 11 (11q13) is responsible for the disease in most patients.  Best disease is usually transmitted in an autosomal dominant pattern from parent to offspring.  A large number of mutations have been found in the BEST1 gene but so far no correlation with severity of disease is possible.  In fact, there is a great deal of clinical variation within families having identical mutations resembling that of the variation found among different mutations.

Several families have also been reported with autosomal recessive inheritance.  Affected offspring had homozygous mutations in the bestrophin gene with reduced light/dark responses and vision loss.  Some have atypical vitelliform retinal and sometimes multifocal lesions.  They may develop angle closure glaucoma.  Their heterozygous parents  have either normal or abnormal EOGs and no visible fundus disease.  So far no families with presumed recessive inheritance of Best macular dystrophy have demonstrated parent-to-child transmission of typical vitelliform lesions.

Genotyping has identified at least 5 forms of vitelliform macular dystrophy.  In addition to the iconic Best disease described here we know of at least four more variants and specific mutations have been identified in three.  No mutation or locus has yet been identified in VMD1 (153840) but it is likely a unique condition since mutations in other genes known to cause vitelliform dystrophy have been ruled out.  Other forms are VMD3 (608161) due to mutations in the PRPH2 gene, VMD4 (616151) resulting from mutations in the IMPG1 gene, and VMD5 (616152) caused by mutations in the IMPG2 gene.

Autosomal dominant vitreoretinochoroidopathy (193220) is an allelic disorder.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

None known for disease.  Subretinal neovascularization may benefit from ablation treatments.

References
Article Title: 

Mutations in IMPG1 Cause Vitelliform Macular Dystrophies. Am

Manes G, Meunier I, Avila-Fern?degndez A, Banfi S, Le Meur G, Zanlonghi X, Corton M, Simonelli F, Brabet P, Labesse G, Audo I, Mohand-Said S, Zeitz C, Sahel JA, Weber M, Dollfus H, Dhaenens CM, Allorge D, De Baere E, Koenekoop RK, Kohl S, Cremers FP, Hollyfield JG, S?(c)n?(c)chal A, Hebrard M, Bocquet B, Garc??a CA, Hamel CP. Mutations in IMPG1 Cause Vitelliform Macular Dystrophies. Am J Hum Genet. 2013 Aug 29. [Epub ahead of print] PubMed PMID: 23993198.

PubMed ID: 
23993198

Biallelic mutation of BEST1 causes a distinct retinopathy in humans

Burgess R, Millar ID, Leroy BP, Urquhart JE, Fearon IM, De Baere E, Brown PD, Robson AG, Wright GA, Kestelyn P, Holder GE, Webster AR, Manson FD, Black GC. Biallelic mutation of BEST1 causes a distinct retinopathy in humans. Am J Hum Genet. 2008 Jan;82(1):19-31. PubMed PMID: 18179881

PubMed ID: 
18179881

Identification of the gene responsible for Best macular dystrophy

Petrukhin K, Koisti MJ, Bakall B, Li W, Xie G, Marknell T, Sandgren O, Forsman K, Holmgren G, Andreasson S, Vujic M, Bergen AA, McGarty-Dugan V, Figueroa D, Austin CP, Metzker ML, Caskey CT, Wadelius C. Identification of the gene responsible for Best macular dystrophy. Nat Genet. 1998 Jul;19(3):241-7.

PubMed ID: 
9662395
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