How Whole Exome Sequencing Helps Diagnose Costello Syndrome


A diagnosis is something that is not always easy to attain. Without one, people cannot receive the best treatment for their conditions, miss out on a community of others with their condition, and may simply feel frustrated and frightened. A new genetic test, called whole exome sequencing, aims to change the amount of people who go without a diagnosis. This test is more successful and looks for thousands of rare conditions, unlike other tests that only look for one. It is being used in England, where it has been used on 80 children so far. One of these children is Henry Dunn, who received a diagnosis of Costello syndrome.

About Costello Syndrome

Costello syndrome is a disorder that affects many parts of the body and is characterized by intellectual disabilities and delayed development. Those with Costello syndrome are also at a heightened risk of developing tumors, both benign and malignant. Mutations in the HRAS gene cause this condition. The protein produced by this gene leads to continuous cell growth and division. If it is inherited, it is passed down in an autosomal dominant pattern, but it usually mutates spontaneously.

Symptoms of this syndrome include loose folds of skin, unusually flexible joints, coarse facial features, heart problems, short stature, slow growth, difficulties with feeding, a tight Achilles tendon, weak muscle tone, skeletal abnormalities, Chiari I malformation, dental and ocular problems, intellectual disabilities, developmental delays, and a heightened risk of tumors.

As these symptoms overlap with many other conditions, it is difficult to diagnose Costello syndrome. A clinical examination and list of specific diagnostic conditions have been developed to aid in diagnosis, but genetic testing is necessary to confirm a diagnosis.

Once a diagnosis is confirmed, treatment is symptomatic. Any cardiac symptoms may be treated with medications, such as beta-blockers. Bracing and occupational and physical therapy are also recommended. Any other symptoms that arise should be handled by a specialist, especially if tumors are malignant.

Henry’s Story

Henry was diagnosed through whole exome sequencing at 20 months old, after experiencing long hospital stays without a diagnosis. It only took a week for this new test to show that he had Costello syndrome.

Because doctors knew that Costello syndrome put Henry at a heightened risk of developing cancer, they were able to monitor and quickly diagnose him. Doctors detected cancer early on the two separate occasions that it developed, and they were able to treat it successfully both times. Henry is now four and in remission.

His mother credits whole exome sequencing as the reason that he was able to receive a diagnosis and the reason his cancer treatment was so effective.

About Whole Exome Sequencing

Whole exome sequencing looks for genetic mutations in the DNA, and it can effectively identify thousands of conditions. Eighty children in England have been tested with it since October, and slightly less than half of them were given a diagnosis. Children who have prolonged stays in the hospital after birth or those in the pediatric ICU may be given this test if doctors suspect that they have a genetic condition.

The test looks for mutations in the genes that provide instructions for proteins. A blood sample is typically what is used. As other genetic tests only look for one condition; the process takes much longer as multiple tests must be administered. Other tests are also only successful 20% of the time, compared to the 46% success rate of whole exome sequencing. Another perk of this test is that it can show if one is unlikely to respond to a specific treatment, which can save a lot of time and money.

Doctors hope to continue to utilize this test to help those with genetic diseases. Their goal is to test up to 700 children each year with whole exome sequencing.

Find the original article here.

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