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Newswise Genetic mutations may cause more cases of amyotrophic lateral sclerosis (ALS) than scientists previously had realized, according to researchers at Washington University School of Medicine in St. Louis and Cedars-Sinai Medical Center in Los Angeles. The scientists also showed that the number of mutated genes influences the age when the fatal paralyzing disorder first appears.

ALS, also known as Lou Gehrigs disease, destroys the nerve cells that control muscles, leading to loss of mobility, difficulty breathing and swallowing, and eventually paralysis and death. Understanding the many ways genes contribute to ALS helps scientists seek new treatments.

The study appears online in Annals of Neurology.

Scientists have linked mutations in more than 30 genes to ALS. Alone or in combination, mutations in any of these genes can cause the disease in family members who inherit them.

Roughly 90 percent of patients with ALS have no family history of the disease, and their condition is referred to as sporadic ALS. Scientists had thought mutations contributed to barely more than one in every 10 cases of sporadic ALS.

But researchers recently started to suspect that patients with sporadic ALS carry mutations in the 30 genes linked to ALS more often than previously thought. The new study is among the first to prove this suspicion correct.

To our surprise, we found that 26 percent of sporadic ALS patients had potential mutations in one of the known ALS genes we analyzed, said co-senior author Matthew Harms, MD, assistant professor of neurology at Washington University. This suggests that mutations may be contributing to significantly more ALS cases.

The scientists used a sequencing technique devised at Washington University to look at 17 known ALS genes in the DNA of 391 patients with ALS. Like the overall ALS patient population, 90 percent of the patients had no family history of disease.

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Genetic Errors Linked to More ALS Cases Than Scientists Had Thought