Scientists searching for a single, simple genetic answer responsible for keratoconus have been disappointed, but as our understanding of genetic associations increases, researchers have been able to make the association between KC and a range of other diseases – some vision-related and some related to other medical conditions. A thorough literature review was recently published in the journal, Ophthalmology and Therapy. The authors concluded that most cases of KC are likely the combination of a keratoconus-susceptibility gene and a secondary influence which could be environment, eye rubbing, allergies, or some other aggravating factor. For instance, the authors found locations with lots of sunshine and hot weather like India and the Middle East tend to be associated with a higher prevalence of KC, than locations with cooler climates and less sunshine: rates of KC range from 0.3/100,000 in Russia to 2,300/100,000 in Central India.
The authors identified 24 genes that are potential contributors to KC, and another 49 genes that had an association to KC symptoms, while primarily associated with other syndromes or diseases. Some of the strongest connections were between genes that also were linked to glaucoma, cataract, Down syndrome, connective tissue disorders, rheumatoid arthritis, mitral valve prolapse, and atopic disease like allergies or asthma.
The authors concluded that awareness of these potential co-morbities should encourage doctors to monitor patients and refer them for evaluation of other conditions when appropriate. One important take-away from this paper is that due to the dominant pattern of inheritance, the increase in KC among close relatives is 15-60x higher than the general population. First degree relatives (parents, children and grandchildren) should be screened for KC and checked for symptoms at annual exams. Read the article, Genetic Aspects of Keratoconus: a Literature Review Exploring Potential Genetic Contributions and Possible Genetic Relationships with Comorbities here.