Cataracts (opacities in the lens of the eye) are caused by many mechanisms. Those present at birth are called congenital and a significant proportion of these are inherited. Those caused by mutations on the X chromosome are known as X-linked.
X-linked congenital cataracts are present at birth and are most dense in males. However, carrier females, such as the mothers of such boys, may have small, dot-like opacities. Males may also have facial and dental malformations in which case the disorder is called Nance-Horan syndrome. At this time it is uncertain if individuals without such additional characteristics have the same disorder as those with the facial features. Some individuals with congenital cataracts also have small corneas (the windshield of the eye) and even small eyeballs.
These cataracts are caused by mutations carried on the X chromosome. Males do not have affected male children but their daughters all inherit the mutant X chromosome and are called carriers (heterozygotes). Such females can expect that half their sons will inherit the mutation causing this type of cataract.
To allow the visual system to mature properly, the dense cataracts in males must be removed soon after birth. Life expectancy is normal