microcornea

Microcornea, Myopia, Telecanthus and Posteriorly-Rotated Ears

Clinical Characteristics
Ocular Features: 

Small corneas measuring 9.8 – 10.5 mm are characteristic.  Acuity is usually 20/60 or better in older children but even younger children maintain steady fixation.  Refractive errors of -6 to -12.75 diopters are usually present but may be much less in other children.  Axial lengths range from 22.42 to 26.84 mm corresponding to the amount of myopia.  The degree of myopic chorioretinal change correlates roughly with the amount of axial myopia.  Telecanthus is present in all individuals.  

Systemic Features: 

The ears are rotated posteriorly.

Genetics

Five males with this syndrome occurred in four consanquineous/endogamous Saudi families suggesting autosomal recessive inheritance.  Homozygous mutations in ADAMTS18 (16q23.1) have been found in these four families.  However, one child had a similarly affected father suggesting to some that this may be a pseudodominant disorder.

Mutations in the same gene are responsible for Knobloch syndrome 2 (KNO2) (608454).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported although correction of the refractive error should be made in early childhood.  It would seem prudent to monitor the vitreoretinal system for further degeneration.

References
Article Title: 

Cataracts, Congenital with Sclerocornea and Glaucoma

Clinical Characteristics
Ocular Features: 

The ocular features are evident at birth or within the first year of life and may be asymmetrical.  The phenotype is heterogeneous but does not appear to be progressive.  The anterior chambers are of normal depth and the fundi are normal when visualization is possible.  The corneal opacification is usually denser peripherally and resembles corneoscleralization but it can extend centrally to a variable degree.  In individuals with glaucoma and buphthalmos the cornea is more opaque and usually vascularized. In such eyes the cornea is thinned.  In most patients the corneal diameters were 5-8 mm in diameter but in those with elevated pressures the anterior segment was obviously buphthalmic. Iridocorneal adhesions may be present.  The lenses are cataractous but the capsules are normal.  Microphthalmia has been reported in some patients.  Vision is often in the range of hand motions.    

Systemic Features: 

None.

Genetics

Homozygous mutations in PXDN (2p25.3) encoding peroxidasin are believed responsible for this autosomal recessive condition.  Mammalian peroxidasin localizes to the endoplasmic reticulum but is also found in the extracellular matrix and is believed important to the maintainence of basement membrane integrity.  The protein is one of several that aids in the extracellular breakdown of hydrogen peroxide and free radicals.  In mouse eyes it localizes to the corneal and lens epithelium but its role in maintaining transparency of the lens and cornea is unknown.

See also Cataracts, Congenital Zonular Pulverulent 1 (116200) in this database for a condition with a similar phenotype but caused by heterozygous mutations in the GJA8 gene.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No information regarding treatment is available but cataract and corneal surgery may be beneficial.   

References
Article Title: 

Novel mutations in PXDN cause microphthalmia and anterior segment dysgenesis

Choi A, Lao R, Ling-Fung Tang P, Wan E, Mayer W, Bardakjian T, Shaw GM, Kwok PY, Schneider A, Slavotinek A. Novel mutations in PXDN cause microphthalmia and anterior segment dysgenesis. Eur J Hum Genet. 2014 Jun 18. doi: 10.1038/ejhg.2014.119. [Epub ahead of print] PubMed PMID: 24939590.

PubMed ID: 
24939590

Homozygous mutations in PXDN cause congenital cataract, corneal opacity, and developmental glaucoma

Khan K, Rudkin A, Parry DA, Burdon KP, McKibbin M, Logan CV, Abdelhamed ZI, Muecke JS, Fernandez-Fuentes N, Laurie KJ, Shires M, Fogarty R, Carr IM, Poulter JA, Morgan JE, Mohamed MD, Jafri H, Raashid Y, Meng N, Piseth H, Toomes C, Casson RJ, Taylor GR, Hammerton M, Sheridan E, Johnson CA, Inglehearn CF, Craig JE, Ali M. Homozygous mutations in PXDN cause congenital cataract, corneal opacity, and developmental glaucoma. Am J Hum Genet. 2011 Sep 9;89(3):464-73.

PubMed ID: 
21907015

Coloboma, Isolated

Clinical Characteristics
Ocular Features: 

Colobomas of the uveal tract are often found in association with other ocular anomalies including those with systemic disease. They are usually located in the inferonasal quadrant as a result of defective closure of the embryonic fissure in the optic cup.  Most involve the nearly complete iris and resemble a keyhole but they may also be partial resulting in an oval pupil.  They are sometimes unilateral in which case the involved iris may be more heavily pigmented than the contralateral one.  They may involve only the iris (simple coloboma) but often are more extensive with involvement of the ciliary body, retina, lens, choroid, and even the optic nerve.  They are frequently associated with microphthalmia (or microphthalmia with cyst [5.6%]) and microcornea (79%). 

Systemic Features: 

None by definition.

Genetics

Isolated colobomas are clinically and genetically heterogeneous resulting from mutations in SHH (7q36.3), PAX6 (11p13), and ABCB6 (2q35) among others.  Large pedigrees with typical autosomal dominant transmission patterns have been reported.

Homozygous mutations in SALL2 (14q11.1-q12.1) have also been reported in patients with isolated colobomas.  Studies of sall2-deficient mice show defects in closure of the anterior optic fissure while posterior closure proceeds normally.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Simple iris colobomas usually do not require treatment.  The visual prognosis depends upon the structures involved.  Those with microcornea usually have a lower acuity and, of course, eyes with the most extensive involvement of the uveal tract and/or the optic nerve may have the least vision. Low vision aids can be helpful in selected individuals.

References
Article Title: 

Mutation of SALL2 causes recessive ocular coloboma in humans and mice

Kelberman D, Islam L, Lakowski J, Bacchelli C, Chanudet E, Lescai F, Patel A, Stupka E, Buck A, Wolf S, Beales PL, Jacques TS, Bitner-Glindzicz M, Liasis A, Lehmann OJ, Kohlhase J, Nischal KK, Sowden JC. Mutation of SALL2 causes recessive ocular coloboma in humans and mice. Hum Mol Genet. 2014 Jan 12. [Epub ahead of print].

PubMed ID: 
24412933

ABCB6 Mutations Cause Ocular Coloboma

Wang L, He F, Bu J, Liu X, Du W, Dong J, Cooney JD, Dubey SK, Shi Y, Gong B, Li J, McBride PF, Jia Y, Lu F, Soltis KA, Lin Y, Namburi P, Liang C, Sundaresan P, Paw BH, Li DY, Phillips JD, Yang Z. ABCB6 Mutations Cause Ocular Coloboma. Am J Hum Genet. 2012 Jan 13;90(1):40-8.

PubMed ID: 
22226084

Blue Diaper Syndrome

Clinical Characteristics
Ocular Features: 

A single patient has been reported with microcornea, optic nerve hypoplasia, and 'abnormal' eye movements.  The full ocular phenotype is unknown but 'visual problems' are sometimes mentioned in other reports.

Systemic Features: 

Nephrocalcinosis and blue urine are the major systemic manifestations of blue diaper syndrome.  Symptoms of fever, constipation, poor weight gain, failure to thrive, and irritability can also be part of the syndrome.

Genetics

This is considered an autosomal recessive disorder although an X-linked defect cannot be ruled out since reported patients have been male.  Parental consanguinity is present in some families.  Nothing is known about the mutation or its locus.  Intestinal transport of tryptophan is defective and bacterial degradation results in excessive indole production.  Oxidation in the urine to indigo blue results in the characteristic discoloration.        

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Restriction of dietary tryptophan has been suggested.

References
Article Title: 

Chorioretinopathy with Microcephaly 1

Clinical Characteristics
Ocular Features: 

The ocular features have not been well described.  Small corneas, hyperopia, pale optic nerves and a variety of pigmentary changes in the retina have been reported.  The latter may consist of diffuse, fine or granular pigmentary changes.  Areas of pigmentary atrophy are often associated with patchy areas of pigmentary clumping.  These changes are usually located posterior to the equator.  Choroidal vessels may be sparse where the RPE is absent.  It has been suggested that the patchy pattern of retinal pigmentation resembles ocular toxoplasmosis.  Strabismus is common.  One report suggests microphthalmos in a patient.  Vision has been reported as subnormal from the first year of life but no quantitative data are available.

Systemic Features: 

Microcephaly is a consistent feature.  The forehead is steeply sloped but facial size appears normal.  The palate is highly arched.  Patients often have hyperactive deep tendon reflexes and walk with a shuffling gait.  Children are often hyperactive and highly social.  Intelligence quotients are usually subnormal. No lymphedema has been reported.  At least some patients have cutis marmorata.

On MRI diffuse pachygryria is seen.  The vermis is hypoplastic and the surface area of the corpus callosum is reduced to half of normal. 

Genetics

 Parental consanguinity was present in two reported families and pedigrees are consistent with autosomal recessive inheritance with homozygous mutations of TUBGCP6 (22p22) responsible.

This presumed recessive disorder appears to be different than the autosomal dominant disorder of lymphedema, microcephaly, and chorioretinal dysplasia  (MCLMR(152950) although molecular confirmation is lacking.

For somewhat similar disorder see Chorioretinopathy with Microcephaly 2 (616171).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Treatment is supportive.

References
Article Title: 

Genetic mapping and exome sequencing identify variants associated with five novel diseases

Puffenberger EG, Jinks RN, Sougnez C, Cibulskis K, Willert RA, Achilly NP, Cassidy RP, Fiorentini CJ, Heiken KF, Lawrence JJ, Mahoney MH, Miller CJ, Nair DT, Politi KA, Worcester KN, Setton RA, Dipiazza R, Sherman EA, Eastman JT, Francklyn C, Robey-Bond S, Rider NL, Gabriel S, Morton DH, Strauss KA. Genetic mapping and exome sequencing identify variants associated with five novel diseases. PLoS One. 2012;7(1):e28936. Epub 2012 Jan 17. PubMed PMID: 22279524.

PubMed ID: 
22279524

Chorioretinal dysplasia, microcephaly, and mental retardation

Clinical Characteristics
Ocular Features: 

The ocular phenotype has not been well defined in this condition since few families have been reported.  Microphthalmia is present in some patients.  The corneas may be small and there is often some conjunctival growth over the limbus.

The retinal features consist of lacunar depigmentation of the RPE and in some cases resemble the lesions of congenital toxoplasmosis.  Eighty to 90 per cent of patients have areas of atrophic and dysplastic-appearing lesions of the retina and choroid with vascular attenuation.  The edges of lacunae may have patchy hyperpigmentation.  These lesions are usually static but may show mild progression.  Visual acuity is generally stable or only mildly progressive.  However, other patients have a severe reduction in acuity.  ERG responses are reduced.

Systemic Features: 

The amount of microcephaly may be minimal and at least some patients have 'bulging' foreheads.  The amount of mental deficiency varies from mild to severe.  IQ levels are generally in the range of 60-70.   Hypotonia has been reported in more severe cases.  Skull size is usually 2-3 standard deviations below the mean and generally has some frontal prominence.

Genetics

This seems to be an autosomal dominant disorder although no loci or mutations have been identified.  It is likely that the category of disease known as microphthalmia-chorioretinal syndrome consists of a heterogeneous group of disorders.  No locus or specific mutation has been identified.

It differs from the microcephaly, lymphedema, chorioretinopathy syndrome (152950) in which retinal folds, ptosis and lymphedema are associated with a typical facial phenotype.  For other disorders in this database having a somewhat similar phenotype see: chorioretinopahty and microcephaly type 1 (251270) and type 2 (616171).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Treatment is supportive.  Low vision aids may be helpful.

References
Article Title: 

Microphthalmia, Syndromic 8

Clinical Characteristics
Ocular Features: 

Microphthalmia is a consistent feature and short palpebral fissures have been described in one patient.  Microcornea has also been noted.  At least one patient was blind.

Systemic Features: 

The skull is small and mental retardation is usually a feature.  Other variable abnormalities include cardiac defects, prognathism, split-feet, cryptorchidism, and cleft lip and palate.  Few patients have been reported and the full phenotype is unknown.

Genetics

The gene remains unidentified in this rare syndrome but a locus has been identified at 6p21.  In at least one patient with a balanced translocation of t(6;13)(q21;q12) a disruption in the SNX3 gene at 6q21 was identified.  Most cases occur sporadically and have cytogenetic abnormalities.

Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Microphthalmia, Syndromic 7

Clinical Characteristics
Ocular Features: 

Microphthalmia and rarely clinical anophthalmia are the ocular hallmarks of this disorder.  Corneal leukomas and some degree of sclerocornea are usually present as well.  Orbital cysts have been observed.  Other less consistent findings include iridocorneal adhesions, glaucoma, microcornea, cataracts, aniridia, persistence of the anterior hyaloid artery and other vitreous opacities, and patchy hypopigmentation of the RPE.

Systemic Features: 

The skin on the nose, cheeks and neck has linear red rashes and scar-like lesions.  Biopsy of these has revealed smooth muscle hemartomata rather than simple dermal aplasia.  There may be some healing of the skin defects.  The corpus callosum is sometimes absent.  Diaphragmatic hernias are often present.  Cardiac abnormalities include hypertrophic cardiomyopathy, arrhythmias, and septal defects.   Preauricular pits and hearing loss have been found in some patients.  Patients may be short in stature and some have nail dysplasia.  GU and GI anomalies may be present.

Genetics

This is an X-linked dominant disorder with lethality in the hemizygous male.  Many patients (79%) have interstitial deletions of the Xp22.2 region of the X chromosome.  Sequence analysis of this region has revealed heterozygous point mutations in the HCCS gene (Xp22.2) in numerous other patients.  In several additional cases deleterious mutations have been found in the X-linked COX7B gene.  However, familial occurrence is uncommon.  X chromosome inactivation may be skewed with the abnormal X being inactive in virtually all cases. Several 46 XX males with this syndrome have been described.

Goltz syndrome (305600), also called focal dermal hypoplasia, may have similar skin and ocular findings but the limb anomalies are not found in the disorder described here.  Goltz syndrome (305600) is the result of mutations in PORCN at another locus on the X chromosome and is thus unrelated.

Other X-linked dominant disorders with lethality in hemizygous males and abnormalities in skin and the eye are Incontinentia pigmenti (308300) and Aicardi syndrome (304050).  The skin lesions and ocular anomalies are dissimilar to those in MLS and they often have far more severe CNS abnormalities.   Further, the mutation causing Aicardi is in the NEMO (IKBKG) gene at another location on the X chromosome.

Pedigree: 
X-linked dominant, mother affected
Treatment
Treatment Options: 

Treatment is organ-specific with repair of septal defects and diaphragmatic hernias.  Progressive orbital prosthetics should be considered in patients with blind, microphthalmic and clinically anophthalmic eyes.

References
Article Title: 

Microphthalmia with linear skin defects syndrome in a mosaic female infant with monosomy for the Xp22 region: molecular analysis of the Xp22 breakpoint and the X-inactivation pattern

Ogata T, Wakui K, Muroya K, Ohashi H, Matsuo N, Brown DM, Ishii T, Fukushima Y. Microphthalmia with linear skin defects syndrome in a mosaic female infant with monosomy for the Xp22 region: molecular analysis of the Xp22 breakpoint and the X-inactivation pattern. Hum Genet. 1998 Jul;103(1):51-6. Review.

PubMed ID: 
9737776

Anterior Segment Mesenchymal Dysgenesis

Clinical Characteristics
Ocular Features: 

The unique status of this entity remains to be established as there are overlapping features with aniridia (106210), and Peters anomaly (604229), posterior embryotoxon, and iridogoniodysgenesis type 1 (601631) and type 2 (137600).  Anterior segment mesenchymal dysgenesis itself is clinically heterogeneous even within families.  Schwalbe line is often anteriorly placed and there may be iris adhesions to the cornea, with or without corneal opacities.  Some patients have microcornea.  All layers of the cornea are dysplastic from the epithelium to the endothelium suggesting abnormal migration or function of neural crest cells.  Lens opacities are highly variable but they can be progressive. Curiously, elevated intraocular pressure is usually not present.  Visual acuity is highly variable with some patients having 20/20 vision and others bare hand motions depending on the degree of opacification of the lens and cornea.

Systemic Features: 

No systemic abnormalities are present.

Genetics

This is an autosomal dominant disorder secondary to mutations in either PITX3 (10q24.32) or FOXE3 (1p32)  which are both transcription factors.  The latter gene is also mutant in congenital primary aphakia (610256) and some cases of Peters anomaly (604229).

See also Anterior Segment Dysgenesis 6 (617315) and Anterior Segment Dysgenesis 8 (617319) for autosomal recessive conditions in which mutations result in malformations of the anterior chamber.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Cataract surgery is indicated in some cases and corneal transplantation has been attempted in a few individuals.

References
Article Title: 

Cataracts, Congenital Zonular Pulverulent 1

Clinical Characteristics
Ocular Features: 

Bilateral lens opacities may be both nuclear and zonular.  The embryonic and fetal nuclei are usually involved and diffuse cortical opacities may also be seen in some patients.  The involved area is therefore larger than the somewhat similar Coppock-like cataract (604307) which is limited to the embryonic nucleus.  The lens opacities may be seen at birth or in early childhood and usually progress. There is considerable clinical variation in the degree and distribution of the usual dust-like opacities which may also be lamellar in distribution with a clear peripheral cortex and minimal nuclear involvement.  Microcornea has also been reported.  In mild cases the lens opacities are primarily clustered along the Y sutures resembling congenital zonular cataracts with sutural opacities (600881).

Three unrelated patients with mutations in GJA8 and total sclerocornea have been reported.  Two of these patients in addition had small abnormal lenses while the third had cataracts and micropthalmia.  Two of the three also develped glaucoma by one year of age.

The nature and morphology of the lens opacities in an adult have been studied by light and scanning electron microscopy.  They are located in the embryonic and fetal nuclei and appear "puffy" with lens fiber irregulaties and entanglement in adjacent areas. 

Systemic Features: 

None.

Genetics

Congenital zonular pulverulent cataracts are inherited in an autosomal dominant pattern resulting from missense mutations in the GJA8 gene (1q21.1) that codes for connexin 50.  These belong to a category of lens opacitites now designated "Cataract 1, Multiple Types" in OMIM (116200). They have been detected in multiple populations and ethnic groups around the world.

Mutations in CZP3 at 13q11-13 coding connexin 46 (601885) result in a similar phenotype (Cataracts, Congenital Zonular Pulverulent 3) suggesting that genetic heterogeneity is present.

This was the first disease locus to be linked on a human autosome, in this case to the Duffy blood group locus on chromosome 1.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Cataract surgery is indicated for visually significant lens opacities which may be required late in the first or early in the second decade of life.

References
Article Title: 

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