Jan. 17 (HealthDay News) -- Genetic differences might explain why some multiple sclerosis (MS) patients respond to treatment while others don't, suggests an international study.

Starting with 206 southern European patients with relapsing-remitting MS, the most common form of the disease, the researchers compared the DNA of patients whose symptoms were reduced by interferon beta therapy to the DNA of those who experienced relapses after such therapy. They were able to identify important genetic differences between the two groups of patients.

Those differences could eventually be used to help predict which MS treatments will benefit which patients, the study authors said. MS is a neurological disorder in which nerve fiber coatings degenerate, which leads to muscle weakness and possible paralysis.

The findings appeared in the Jan. 14 online issue of the Archives of Neurology and were expected to be published in the March print issue of the journal.

"The beneficial outcomes of interferon beta therapy for patients in the relapsing-remitting phase of MS have been clearly shown," the researchers wrote. "On the other hand, the effect of this treatment is partial, and a substantial amount of patients (up to 50 percent) are not responders. Hence, in the absence of prognostic clinical, neuroradiological and/or immunological markers of response, the question remains who and when to treat when adverse effects, inconvenience and the cost of drugs are significant."

More research is needed to fully predict MS treatment outcomes based on patient DNA analysis, the researchers added.

SOURCE: JAMA/Archives journals, news release, Jan. 14, 2008