SynopsisCodesDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsDrug Reaction DataReferences
Immune-mediated necrotizing myopathy
Other Resources UpToDate PubMed

Immune-mediated necrotizing myopathy

Contributors: Benjamin L. Mazer MD, MBA
Other Resources UpToDate PubMed


Immune-mediated necrotizing myopathy (IMNP) is a recently described, very rare inflammatory myopathy in the same category as dermatomyositis and polymyositis. Like those diseases, it presents with proximal muscle weakness and elevated muscle enzymes. IMNP is caused by autoantibodies that recognize "anti-signal recognition particle." A small number of cases are attributed to statin use producing antibodies to HMG-CoA reductase.

Muscle biopsy shows muscle fiber necrosis without inflammatory cells.

Immunosuppressive medications, including corticosteroids, intravenous immunoglobulin (IVIG), and rituximab, are used to treat the disease. Statins should be discontinued in cases associated with these drugs.


G72.49 – Other inflammatory and immune myopathies, not elsewhere classified

715863001 – Autoimmune necrotizing myopathy

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

  • Dermatomyositis
  • Polymyositis
  • Steroid myopathy
  • Electrolyte abnormality (eg, Hypocalcemia, Hypokalemia)
  • Myasthenia gravis
  • Inclusion body myositis
  • Giant cell myositis
  • Eosinophilic myositis
  • Mitochondrial myopathy
  • Peripheral neuropathy
  • Radiculopathy (eg, Lumbar radiculopathy)
  • Spinal stenosis (see Cervical spinal stenosis, Lumbar spinal stenosis)
  • Muscular dystrophy (eg, Limb-girdle muscular dystrophy, Duchenne muscular dystrophy)
  • Amyotrophic lateral sclerosis
  • Drug-induced myopathies (eg, antifungals, antimalarials, corticosteroids)
  • Hypothyroidism
  • Cushing syndrome
  • Systemic lupus erythematosus
  • Mixed connective tissue disease
  • CREST syndrome
  • Trichinellosis
  • Polymyalgia rheumatica
  • Primary hyperparathyroidism

Best Tests

Subscription Required

Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

Subscription Required


Subscription Required

Last Updated:04/27/2023
Copyright © 2024 VisualDx®. All rights reserved.
Immune-mediated necrotizing myopathy
A medical illustration showing key findings of Immune-mediated necrotizing myopathy : Proximal muscle weakness, Symmetric extremities distribution, HMG-CoA reductase inhibitor, Dyspnea, CPK elevated
Copyright © 2024 VisualDx®. All rights reserved.