Whole‐exome sequencing emerges as clinical diagnostic tool

UPDATE W hole-exome sequencing (WES) can be a useful diagnostic tool outside of research settings, a recent study shows.Using WES testing methods, researchers at the Baylor College of Medicine in Houston, Texas, were able to diagnose 25% of 250 previously undiagnosed patients with suspected genetic disorders, according to a recent paper published in the New England Journal of Medicine [Yang et al, 2013].As many as 80% of the patients were children with neurologic symptoms.In all, scientists identifi ed 86 mutated genes that are known to cause genetic diseases in 62 of the 250 patients.The overall diagnostic yield of 25% is higher than that of more established genetic tests, such as karyotype and chromosomal microarray, which provide answers in 15% to 20% of cases, say researchers. What Was RevealedAmong the 62 patients who received a diagnosis, 33 had autosomal dominant disease, 16 had autosomal recessive disease, and 9 had X-linked disorders.Four patients received two distinct molecular diagnoses that challenged previous determinations of disease based on history and physical exam.A total of 83% of the autosomal dominant mutant alleles and 40% of X-linked mutant alleles occurred de novo, say researchers."There are thousands of genetic conditions, some of which are very, very rare," says senior author Christine M.