title: Long-term muscular outcome and predisposing and prognostic factors in juvenile dermatomyositis: A case-control study.
abstract: OBJECTIVE
  To compare muscle strength, physical health, and HLA-DRB1 allele carriage frequencies in patients with longstanding juvenile dermatomyositis (DM) with that of controls, and to determine the presence of and risk factors for muscle weakness and magnetic resonance imaging (MRI)-detected muscle damage in juvenile DM patients.
  
  
  METHODS
  Fifty-nine patients with juvenile DM examined a median of 16.8 years (range 2.0-38.1 years) after disease onset were compared with 59 age- and sex-matched controls. Muscle strength/endurance was measured by manual muscle testing (MMT) and the Childhood Myositis Assessment Scale (CMAS); health status was measured by the Short Form 36. HLA-DRB1 alleles were determined by sequencing in patients and 898 healthy controls. In patients, disease activity/damage was measured by the Disease Activity Score (DAS), Myositis Damage Index (MDI), Health Assessment Questionnaire/Childhood Health Assessment Questionnaire, and MRI scans of the thigh muscles. Early disease characteristics were obtained by chart review.
  
  
  RESULTS
  Patients had lower muscle strength/endurance (P < 0.001 for both) and physical health (P = 0.014) and increased HLA-DRB1*0301 (P = 0.01) and DRB1*1401 (P = 0.003) compared with controls. In patients, persistent muscle weakness was found in 42% with MMT (score <78) and in 31% with the CMAS (score <48), whereas MRI-detected muscle damage was found in 52%. Muscle weakness and MRI-detected muscle damage were predicted by MDI muscle damage and a high DAS 1 year postdiagnosis.
  
  
  CONCLUSIONS
  A median of 16.8 years after disease onset, juvenile DM patients were weaker than the controls; muscle weakness/reduced endurance was found in 31-42% of patients and MRI-detected muscular damage was found in 52% of patients. The outcomes were predicted by high disease activity and muscle damage present 1 year postdiagnosis.
authors.affiliation: University of Oslo, Oslo University Hospital, Rikshospitalet, Norway. helga.sanner@medisin.uio.no
authors.forename: Helga
authors.initials: H
authors.lastname: Sanner
authors.forename: Eva
authors.initials: E
authors.lastname: Kirkhus
authors.forename: Else
authors.initials: E
authors.lastname: Merckoll
authors.forename: Anita
authors.initials: A
authors.lastname: Tollisen
authors.forename: Mona
authors.initials: M
authors.lastname: Røisland
authors.forename: Benedicte A
authors.initials: BA
authors.lastname: Lie
authors.forename: Eli
authors.initials: E
authors.lastname: Taraldsrud
authors.forename: Jan Tore
authors.initials: JT
authors.lastname: Gran
authors.forename: Berit
authors.initials: B
authors.lastname: Flatø
mesh_terms: D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003882:Dermatomyositis / Q000175:diagnosis*; D004198:Disease Susceptibility; D005260:Female; D006684:HLA-DR Antigens / Q000235:genetics; D059811:HLA-DRB1 Chains; D006304:Health Status; D006801:Humans; D008297:Male; D009043:Motor Activity; D053580:Muscle Strength; D018908:Muscle Weakness / Q000150:complications; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology; D009220:Myositis / Q000175:diagnosis*; D012307:Risk Factors; D012867:Skin / Q000473:pathology; D016896:Treatment Outcome
chemical_list: D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; C553502:HLA-DRB1*03:01 antigen