Because a high percentage of rare diseases have a genetic component, most undiagnosed patients benefit from evaluation at a clinical genetics center where they can receive genetic testing (for a search tool to locate clinical genetics centers in the U.S., please visit the American College of Medical Genetics and Genomics website at: https://clinics.acmg.net.)
Genetic testing involves examining a person’s DNA, the structure in cells that carries the genetic code. This testing can reveal variants, or changes, in genes that can help to diagnose some rare diseases.
Genetic tests can be performed on samples of blood, skin, saliva, or other tissue. These tests can help to confirm a rare disease diagnosis and identify treatment options, including clinical trials. Most genetic tests focus on examining one gene at a time, based on a clinician’s judgement of the most likely cause for a person’s condition.
Although genetic testing often provides a diagnosis, it may be difficult to predict which of the approximately 22,000 genes in the human genome is the cause of a person’s condition.