Solving the Mysteries of Undiagnosed Diseases
In my last blog post, I talked about the value that the $1,000 genome is expected to bring to healthcare. But that doesn’t mean that we have not already seen great benefits from the introduction of whole exome and whole genome sequencing in the clinic. For patients who have spent months – even years – navigating through what many refer to as the “diagnostic odyssey,” or searching for the cause of a prolonged and undiagnosed disease, more advanced genetic testing can help.
Why Exome and Genome Sequencing?
Traditionally, genetic testing has involved testing small numbers of genes at a time. For conditions that are well-described and somewhat common, this works well. However, there are some cases where the common tests don’t come up with an answer. This can lead to patients enduring years of blood tests, imaging studies, failed treatments and huge medical bills without finding the cause of their condition. The ability to sequence the whole genome (the entire genetic sequence of an individual) or the exome (the one percent of our DNA that creates the proteins in the body) allows geneticists and genetic counselors to look for causes of diseases that we may not have been able to find before.
From Exome to Cure
Whole exome and whole genome sequencing started impacting medical care in 2009 with a little boy from Wisconsin named Nicholas Volker, who was diagnosed with a very severe form of inflammatory bowel disease. Nic was four years old, had spent more than 300 days in the hospital, more than 100 trips to the operating room and wasn’t getting better. Despite exhaustive testing, Nic’s doctors did not know what was causing his disease. With no good treatment options, they reached out to a genomics researcher at the Medical College of Wisconsin who agreed to sequence Nic’s exome. By searching through more than 16,000 variations in Nic’s exome, the team of geneticists, genetic counselors and scientists found that a rare variation in an immune system gene was the cause of Nic’s disease. With this knowledge, Nic’s doctors believed that a bone marrow transplant would cure him. They were right and Nic is now nine years old, and doing well.
The ability to sequence the whole genome (the entire genetic sequence of an individual) or the exome (the one percent of our DNA that creates the proteins in the body) allows geneticists and genetic counselors to look for causes of diseases that we may not have been able to find before.
Ending the Diagnostic Odyssey
Nic was the first of many people to benefit from whole exome and whole genome sequencing. Since then, testing has become much less expensive, may be covered by health insurance and is available in several labs nationwide. Whole genome or whole exome sequencing could be considered if:
- The medical and family history strongly indicate that the condition is expected to be genetic.
- Standard genetic testing did not lead to an answer.
- The way that the condition is presenting does not seem to fit with any known and well-described disorders.
Physicians and laboratories that conduct whole genome and whole exome sequencing find an answer in about 30 percent of people who are tested. While this means we still have a ways to go, this type of testing can end the diagnostic odyssey for many.
How Can Genetic Counselors Help?
Many laboratories currently offer whole genome and whole exome sequencing. As a lab-based genetic counselor, it’s my job to help physicians and patients determine if the tests might be helpful for them. Clinical genetic counselors in your community can help review your medical and family history and determine if this type of testing is appropriate in your case, and they can help you get the test covered by insurance. Genetic counselors will also help you understand what testing results mean for you and your family. If you are interested in learning more, find a genetic counselor in your area by using NSGC’s “Find a Genetic Counselor” tool.
To learn more about Nic’s story, read the Pulitzer-Prize winning series by the Milwaukee Journal Sentinel, “One in a Billion: A Boy’s Life, A Medical Mystery.”
Erica Ramos, MS, CGC is a personalized medicine expert for the National Society of Genetic Counselors and is a Senior Genetic Counselor at Illumina, Inc. in San Diego.