OMIM ID:
Microphthalmia with Coloboma, X-Linked
Alternate Names
Defective Genes
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
Inheritance
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 disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked recessive, father affected
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.