While most cases of keratoconus occur in people who have no family history of KC, the disorder does seem to run in certain families.
Keratoconus is an autosomal dominant disease with incomplete penetrance. That means that about half of the children of a person with KC may inherit the gene. Of those who carry the gene, a smaller subset will actually develop the disorder. And since the severity of the disease varies, it is possible that many people go through life without knowing they have KC. They simply believe they need eyeglasses or contact lenses to correct their vision abnormalities.
They found that 80% of the patients reported no close family members with KC. 292 patients (about 20%) said they were aware of other close family members with KC. In other studies, the percentage of patients who claimed a positive family history for KC has ranged from as low as 3% to as high as 28%. Of the 20% in this study who said they had close family members with KC, 53% (159 patients) reported one other family member, and 46% (133 patients) reported 2 or more family members with KC.
The individuals in this study who had other affected family members seemed to have more severe disease (steeper K readings and more astigmatism). The authors recommend that family members of patients with KC should be encouraged to be screened for the disease. Corneal mapping of siblings or other close relatives starting during adolescence may lead to awareness of corneal changes and early intervention. But remember, the majority of patients who develop KC have no apparent genetic links to the disease. A positive family history for KC only accounts for about 1 out of 5 patients with the disease.
Read: Naderan M, et al, “Association between Family History and Keratoconus Severity”, Curr Eye Research, 9:1-5, 2016.