Anti-signal recognition particle (SRP) and anti-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) autoantibodies are closely associated
About
- Autoimmune myopathy
Aetiology
- Myofiber necrosis with minimal inflammatory cell infiltrate
Types of IMNM
- Anti-SRP myopathy
- Anti-HMGCR myopathy
- Antibody-negative IMNM
Clinical
- Severe proximal weakness
- Interstitial lung disease may be seen
Investigations
- Anti-SRP or anti-HMGCR antibodies
- Elevated CK
- Inflammatory muscle biopsies with muscle cell necrosis and muscle cell regeneration
- EMG: myopathic and helps exclude myasthenia
- MRI can show muscle damage
Management
- Muscle prognosis is worse than in most other types of myositis
- Steroids, Methotrexate and Rituximab and IVIG may be used