Corneal Dystrophy, Endothelial X-Linked
Patient Information
Characteristics
Background and History
A number of gene mutations cause corneal dystrophy (degeneration) of various types. This one is unusual as it occurs primarily in males.
Clinical Correlations
The cornea (the normally clear windshield of the eye) is often noted to be cloudy at birth and progressively becomes more so. It has the appearance of ground glass or a milky white cloudiness. The vision is variably affected, from near normal to severe cloudiness or even legal blindness. There is no associated systemic disease.
Genetics
Inheritance
This is a so-called X-linked disorder because the mutation resides on the X chromosome. The corneal disease is therefore generally found only in males although there have been some females with vision problems as well. The condition is passed from a carrier female only to her sons although half of her daughters may inherit the mutant chromosome to become carriers like their mother. This seems to be an X-linked dominant mutation since females with a single mutant X-chromosome often have the disease as well, albeit with less severe manifestations.
An affected male does not pass the disease to his children (his sons get only the Y chromosome from him) but all of his daughters will be carriers and can develop disease since they inherit his sole X-chromosome which, of course, carries the dominant mutation.
Pedigree
X-linked dominant, father affected
X-linked inheritance patterns result when disease-causing mutations are located on the X chromosome. Males have one X chromosome while females have two. A mutation on the male's X chromosome frequently is lethal or renders him unable to reproduce. However, in rare cases when males have children, they can expect that all of then will inherit the condition.
X-linked inheritance patterns result when disease-causing mutations are located on the X chromosome. Males have one X chromosome while females have two. A mutation on the male's X chromosome frequently is lethal or at least renders them unable to reproduce. However, in rare cases when males have children, they can expect that all of then will inherit the condition.
X-linked dominant, mother affected
X-linked inheritance patterns result from mutations located on the X chromosome. Females have two X chromosomes of which only one carries a mutation in X-linked dominant disorders. This usually results in expression of the disease and women with a single mutation have the disorder caused by the mutation. Half of their offspring, male and female, will inherit the mutation. Men, with only one X chromosome, will always have the condition if they inherit the one with the mutation. Men would transmit it to all of their offspring. Without a modifying normal gene on a second X chromosome, X-linked dominant conditions are frequently lethal in such males. The result is a vertical transmission pattern, usually from female to female.
X-linked inheritance patterns result from mutations located on the X chromosome. Females have two X chromosomes of which only one carries a mutation in X-linked dominant disorders. This usually results in expression of the disease and women with a single mutation have the disorder caused by the mutation. Half of their offspring, male and female, will inherit the mutation. Men, with only one X chromosome, will always have the condition if they inherit the one with the mutation. Men would transmit it to all of their offspring. Without a modifying normal gene on a second X chromosome, X-linked dominant conditions are frequently lethal in such males. The result is a vertical transmission pattern, usually from female to female.
Diagnosis and Prognosis
The diagnosis may be suspected in male infants if their corneas are cloudy. Only an ophthalmologist can make the proper diagnosis following a complete eye examination, however, since the appearance of the cornea superficially appears similar to that of other corneal dystrophies. Corneas that are sufficiently cloudy to cause vision problems can be replaced by a clear corneal transplant. The appearance of the cornea resembles that seen in congenital glaucoma and all infants should be evaluated for his condition as well.
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