Abstract
Objective
To determine the long‐term outcome and associated clinical, serologic, and pathologic features in a cohort of patients with connective tissue disease (CTD) and the anti–signal recognition particle (anti‐SRP) autoantibody.
Methods
Sera and clinical data were collected prospectively from consecutive adult patients with polymyositis (PM; n = 134), dermatomyositis (n = 129), or other CTDs (predominantly systemic sclerosis [SSc; n = 790]). Patients were first evaluated during 1973–2001.
Results
Nineteen patients with the anti‐SRP autoantibody were identified, 16 (84%) of whom had pure PM and 3 (2 with SSc and 1 with antisynthetase syndrome) had yet to develop features of myositis after a mean followup of 4.5 years (range 2.5–6 years). More SRP‐positive PM patients had severe proximal muscle weakness (50%) and muscle atrophy (67%) at initial presentation compared with antisynthetase‐positive PM controls. Cardiac involvement occurred in only 2 of 16 SRP‐positive PM patients (13%), and interstitial lung disease was noted in 3 of 13 SRP‐positive PM patients (23%) and in the 3 SRP‐positive nonmyositis patients. There was a relative lack of inflammation in muscle biopsy specimens from the SRP‐positive PM cohort. Other autoantibodies in the SRP‐positive patients included Ro/SSA (4 patients), Th/To (1 patient), and anti–PL‐12 (1 patient). Survival in the SRP‐positive PM patients was comparable with that seen in the cohort of SRP‐negative PM patients.
Conclusion
The anti‐SRP autoantibody is not specific for PM. Severe muscle weakness and atrophy were prominent features in PM patients with anti‐SRP. Cardiac involvement was less common and survival was better in patients with anti‐SRP than has previously been reported.