Many parents wonder why one child is diagnosed with autism while the other is not, and a recent study conducted byBrownUniversitymay have an explanation. There may be a potential genetic variation, causing autism and an intellectual disability, due to “runs of homozygosity,” or blocks of DNA that are passed on from not one, but both parents.
The study was lead by Eric Morrow, assistant professor of biology in the Department of Molecular Biology, Cell Biology, and Biochemistry atBrownUniversity, analyzing the DNA of 2,100 children. The children were born into what is called a “simplex” family, where they are the only one in the family to be diagnosed with autism and an intellectual disability.
According to previous data, many genetic disorders are recessive, and this high run of homozygosity suggests both parents passed on this recessive DNA. Furthermore, this suggests that the parents “may have unwittingly co-inherited these recessive variants from a distant shared relative about which neither parent is aware.” [i]
More than 500 children in the study who had both autism and an intellectual disability (an IQ of 70 or below) showed large runs of homozygosity than their siblings who did not have autism or an intellectual disability. It is important to note that the study does not suggest that runs of homozygosity or recent shared ancestry to be a risk factor for autism. The study is simply suggesting that siblings who do have autism and an intellectual disability have higher runs of homozygosity. In reference to further examination, Morrow commented,
“It could be in the picture where, if you have a person with autism and who has some degree of intellectual disability, and you see also they have large runs of homozygosity, then together you could say that constellation of symptoms might help us predict that they’d be less responsive to conventional treatments and we’d have to discern a new treatment pathway.” [ii]
Hopefully this study will lead to further examination, and potential biomarkers for the diagnosis of autism, and beneficial interventions.
[i] “Brown University” DNA markers in low-IQ autism suggest heredity. 03 Jul 2013. Web. <http://news.brown.edu/pressreleases/2013/07/autism>
[ii] “Brown University” DNA markers in low-IQ autism suggest heredity. 03 Jul 2013. Web. <http://news.brown.edu/pressreleases/2013/07/autism>