coloboma

Microphthalmia with Coloboma, AD

Clinical Characteristics
Ocular Features: 

Isolated colobomatous microphthalmia is uncommon compared with the syndromal conditions of which there are more than 100.  The clinical findings are confined to the eye in this condition.  The globe is abnormally small (defined by some as less than 20 mm in length in at least one eye).   Incomplete penetrance and variable expression are typical but often the cornea is small and may be cloudy with anterior synechiae suggesting that anterior chamber dysgenesis may also be a feature in some cases.  One or both eyes may be involved.  Visual acuity depends on the structures involved.

It is not uncommon for other ocular abnormalities to occur in association with the malformed globes, such as cataracts, microcornea, sclerocornea and optic nerve dysplasia. 

Systemic Features: 

None.

Genetics

The majority of isolated microphthalmos with coloboma are inherited in an autosomal dominant pattern [see also microphthalmia with coloboma, X-linked (MCOPCB1; 300345)].  Reports are mostly of single kinships.  At least 5 additional genes are involved: MCOPCB2 (605738) results from mutations in a locus at 15q12-q15, MCOPCB3 (610092) is caused by mutations in the CHX10 (VSX2) gene (14q24), MCOPCB4 (251505) frequently has a cystic malformation as well and is likely an autosomal recessive condition but the mutation and its location remain unknown, MCOPCB5 (611638) is caused by a mutation in SHH (7q36), and MCOPCB6 (613703) results from mutations in the GDF3 gene (12p13.1).

For an X-linked form of non-syndromic microphthalmia with coloboma, see Microphthalmia with Coloboma (300345 ).  For a syndromal form of X-linked microphthalmia, see Microphthalmia, Syndromic 1 (309800 ). 

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for the basic malformation. 

References
Article Title: 

Microphthalmia with Coloboma, X-Linked

Clinical Characteristics
Ocular Features: 

Isolated colobomatous microphthalmia is caused multiple mutations and usually inherited in an autosomal dominant pattern.  Type 1 is an X-linked disorder with typical features of small eyes, small corneas, colobomas, and elevated intraocular pressures. 

Systemic Features: 

By definition no systemic disease is present. 

Genetics

The combination of colobomas and microphthalmia is found in numerous heritable syndromes but also occurs in isolation.  X-linked syndromes with this combination usually include mental retardation and cataracts but these are absent in the isolated type described here.  A locus on the X chromosome was identified to lie either on the proximal short arm or the proximal long arm but no specific mutation or gene has been identified.  In the single multigenerational reported family, all affected individuals were male except for one female in whom non-random X-inactivation was postulated. 

Syndromal forms of X-linked microphthalmia with coloboma (309800 ) have also been reported.

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

No treatment is available for the malformations but low vision aids should be considered for appropriate individuals. 

References
Article Title: 

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