Researchers have mined the medical records of more than 100 million people and found close to 3,000 associations between single-gene diseases, such as cystic fibrosis, and complex genetic disorders such as autism. The results were published 26 September in Cell1.
The findings suggest that mutations completely disrupting the function of a gene lead to one type of disorder, and milder variants in the same gene may combine to lead to complex genetic disorders. Links between the two types of disorders may help researchers home in on the biological mechanisms underlying complex diseases.
The genetics of single-gene disorders, such as cystic fibrosis and fragile X syndrome, are relatively simple. In contrast, more than 500 candidate genes have been linked to autism, and the strongest of these account for, at most, about 1 percent of cases.
In the new study, researchers looked at eight medical databases from Denmark and the U.S., totaling more than 110 million people. They identified 2,909 statistically significant links between single-gene diseases and complex ones, most of which haven’t been reported before.
For example, they found that people with autism, bipolar disorder or schizophrenia have unusually high rates of Marfan syndrome, a disorder of connective tissue that makes people abnormally tall. People with fragile X syndrome are more likely than the general population to have certain complex disorders, including asthma, psoriasis or recurrent viral infections, suggesting that the syndrome may affect the immune system.
The findings could also help inform association studies — which link common variants with the risk of developing a disorder, the researchers say. In line with this, they found that common variants linked to complex diseases are more likely to be in genes responsible for single-gene disorders than would occur by chance alone.
1: Blair D.R. et al. Cell 155, 70-80 (2013) PubMed