New Study Identifies Gene and Comorbidities of RLS

October 1, 2007

Is neuromyelitis optica (nmo) igg autoantibody unique to NMO or is it expressed in multiple sclerosis (MS) as well? Recent studies have confirmed the autoantibody’s specificity and are shedding more light on how NMO IgG's autoantigen, the water channel aquaporin-4 (AQP4), uniquely behaves in NMO and MS.

Approximately 75% of patients who carry 1 copyof the BTBD9 gene on chromosome 6 were shown tohave an increased risk of restless leg syndrome(RLS) with periodic leg movements in sleep (PLMS)compared with patients who do not have the variant.1 Fifty percent of the study patients with RLSwere carriers, and being a carrier also was associatedwith decreased iron levels.

Furthermore, patients with moderate to severeRLS are at significantly increased risk for developinghypertension, according to David Rye, MD,PhD, professor of neurology at Emory UniversitySchool of Medicine, and colleagues in Iceland. Ryepresented the data at the 21st Annual Meeting of theAssociated Professional Sleep Societies in Minneapolison June 12.

Using a triaxial accelerometer, 861 Icelandic patientswith RLS were examined for 2 to 5 nights forsigns of PLMS. Results showed that risk of hypertensionincreased with PLMS severity. More than50% of patients with more than 30 PLMS per hourhad hypertension.

Although older age and body mass index predictedhypertension status, these factors were notassociated with PLMS. Risk of hypertension alsowas not associated with the a patient's score on theInternational Restless Legs Syndrome Study Grouprating scale or with the duration of RLS symptoms.Rye's team concluded that the PLMS seen in mostpatients with RLS are associated with increased releaseof adrenaline.

The citation for the study is Stefansson H, RyeDB, Hicks A. A genetic risk factor for periodic limbmovements in sleep. N Engl J Med. 2007;357:639-647.