title: Undiagnosed individuals with first-degree relatives with restless legs syndrome have increased periodic limb movements.
abstract: OBJECTIVE
  To evaluate periodic limb movements during sleep (PLMS) in first-degree relatives of both restless legs syndrome (RLS) patients and matched controls without RLS in order to analyze patterns of this motor sign of RLS.
  
  
  METHODS
  First-degree relatives of a consecutive case series of RLS patients and matched community controls without RLS were evaluated for diagnosis of primary RLS and for PLMS as determined by a leg activity meter. The data were analyzed to determine whether or not PLMS rates are higher than expected for RLS subjects in these families, who have mostly milder disease, and family members of early-onset RLS patients not themselves diagnosed with RLS.
  
  
  RESULTS
  PLMS activity in family members was significantly higher for those diagnosed as RLS compared to those diagnosed as not-RLS. This difference was greater for older than younger subjects. In family members older than the median study age (52 years old) who were diagnosed as not-RLS, PLMS were significantly more frequent in those related to an early-onset RLS proband than in those related to either a control or late-onset RLS proband.
  
  
  CONCLUSIONS
  PLMS are elevated even in those with mild RLS and reveal an age-related worsening of the motor component of RLS. PLMS may represent an incomplete expression of RLS tendencies in families of patients with early-onset RLS, but this needs to be confirmed in future longitudinal studies. The increase in PLMS with age, reported in healthy controls, may in fact occur in part as a partial expression of familial or genetic factors associated with RLS.
authors.affiliation: Department of Neuroscience, Baltimore, The Johns Hopkins University School of Art and Sciences, MD, USA.
authors.forename: Paul V
authors.initials: PV
authors.lastname: Birinyi
authors.forename: Richard P
authors.initials: RP
authors.lastname: Allen
authors.forename: Wayne
authors.initials: W
authors.lastname: Hening
authors.forename: Tinna
authors.initials: T
authors.lastname: Washburn
authors.forename: Suzanne
authors.initials: S
authors.lastname: Lesage
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Earley
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis* / Q000235:genetics*; D010641:Phenotype; D017286:Polysomnography; D012148:Restless Legs Syndrome / Q000175:diagnosis* / Q000235:genetics*; D012720:Severity of Illness Index; D013997:Time Factors