title: A longitudinal study of functional disability in a national cohort of patients with polymyositis/dermatomyositis.
abstract: OBJECTIVE
  To analyze changes in functional status and the factors contributing to disability in a national inception cohort of 257 patients with polymyositis/dermatomyositis (PM/DM).
  
  
  METHODS
  Data were gathered from patients' self-reports on questionnaires: one concerning disease- and treatment-related complications, and the other concerning disability, as reflected by a disability index (DI) derived from the Health Assessment Questionnaire (HAQ).
  
  
  RESULTS
  Based on certain characteristics that differentiated disability patterns, 3 groups of patients were identified. Group 1 patients (n = 153) were < or = 60 years old and never had avascular necrosis (AVN) or a vertebral compression fracture (CF), Group 2 patients were > 60 and never had AVN or a vertebral CF, and Group 3 patients reported AVN or a vertebral CF irrespective of age. As measured by the HAQ DI, disability increased very gradually over time in Group 1 patients and more rapidly in Group 2 and Group 3 patients. The increase in disability in patients experiencing AVN was greater than that in patients with similar pre-AVN disease characteristics who did not develop AVN (P = 0.003).
  
  
  CONCLUSIONS
  In this prospective study of disease course and iatrogenic factors related to functional disability in PM/DM, the HAQ DI increased with disease duration. Corticosteroid-related morbidity, as reflected by the development of AVN or CF, significantly contributed to patient-reported functional disability.
authors.affiliation: Division of Allergy and Clinical Immunology, Montreal General Hospital, Quebec, Canada.
authors.forename: A E
authors.initials: AE
authors.lastname: Clarke
authors.forename: D A
authors.initials: DA
authors.lastname: Bloch
authors.forename: T A
authors.initials: TA
authors.lastname: Medsger
authors.forename: C V
authors.initials: CV
authors.lastname: Oddis
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003882:Dermatomyositis / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D004185:Disability Evaluation; D006233:Persons with Disabilities; D018450:Disease Progression; D005260:Female; D006304:Health Status; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010020:Osteonecrosis / Q000150:complications; D017285:Polymyositis / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D011241:Prednisone / Q000008:administration & dosage / Q000627:therapeutic use; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D011241:Prednisone