Rare genetic condition unraveled through exome sequencing

Biotechnology research company, Nigeria
After undergoing batteries of tests without a conclusive diagnosis, Calvin Lapidus underwent exome sequencing at UCLA, which enabled doctors to identify his rare condition, known as Pitt-Hopkins syndrome. Credit: University of California, Los Angeles

In 2012, Calvin Lapidus became the first patient to undergo exome sequencing at UCLA. He was subsequently diagnosed with a rare genetic condition known as Pitt-Hopkins syndrome, which is most commonly characterized by developmental delays, possible breathing problems, seizures and gastrointestinal problems.


What exome sequencing allows doctors to do is to analyze more than 20,000 genes at once, with one simple blood test.

In the past, genetic testing was done one gene at a time, which is time-consuming and expensive.

"Rather than testing one sequential gene after another, exome sequencing saves time, money and effort," said Dr Julian Martinez-Agosto, a paediatrician and researcher at the Resnick Neuropsychiatric Hospital at UCLA.

The exome consists of all the genome's "exons," which is the coding portion of genes. Clinical exome sequencing is a test for identifying disease-causing DNA variants within the 1 percent of the genome which codes for proteins, the exons or flanks the regions which code for proteins.

To date, mutations in the protein-coding parts of genes account for nearly 85 percent of all mutations known to cause genetic diseases, so surveying just this portion of the genome is an efficient and powerful diagnostic tool. Exome sequencing can help detect rare disorders like spinocerebellar ataxia, which progressively diminishes a person's movements, and suggest the likelihood of more common conditions like autism spectrum disorder and epilepsy.


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