WHAT IS AUTOIMMUNE MYOSITIS?

Defining autoimmune myositis

Autoimmune myositis (AIM) is a rare autoimmune rheumatic disease spectrum and a distinct form of myositis, characterized by immune-mediated muscle damage and encompassing a range of heterogeneous clinical subtypes.1,2

 

AIM typically presents with progressive skeletal muscle weakness and variable extramuscular involvement.1,2

AIM: A rare, chronic, progressive autoimmune disease

Autoimmune myositis is a rare, chronic, progressive condition in which immune-mediated inflammation typically leads to skeletal muscle damage and weakness. While symmetrical proximal muscle weakness is a common feature, the disease frequently extends beyond muscle to affect other organ systems.1,2

Disease progression and severity can vary widely, with many patients experiencing significant functional impairment and loss of independence over time.1–3

Shattered blue and white ceramic vase scattered across a wooden floor, with broken pieces spread around the damaged vessel.

The heterogenous spectrum of AIM

AIM comprises a spectrum of clinically and biologically distinct subtypes unified by an underlying autoimmune pathophysiology.3,4

what_is_aim

Continue exploring AIM

Learn more about the growing range of autoantibodies which have been identified across AIM subtypes.

Subtypes and clinical manifestations

Distinct clinical phenotypes exist across the AIM spectrum.3

Learn about the subtypes and manifestations

Abbreviations:
AIM, autoimmune myositis; ASyS, antisynthetase syndrome; DM, dermatomyositis; IBM, inclusion body myositis; IMNM, immune-mediated necrotizing myopathy; OM, overlap myositis; PM, polymyositis.

 

References:
1. Diomedi M, et al. Clin Exp Rheumatol. 2026;44(2):167–177; 2. Oldroyd A, et al. Clin Med (Lond). 2017:17(4):322-328; 3. Paik J, et al. Rheumatol. 2025;64:32883302; 4. Giannini M, et al. Clin Exp Rheumatol. 2025;43(2):178–183; 5. Cleveland Clinic. Myopathy: Causes, Symptoms, Diagnosis & Treatment. https://my.clevelandclinic.org/health/diseases/17256-myopathy. 20 January 2022. Accessed 1 May 2026: 6. Hussain Y, Pokala K. Kuo N. Noninflammatory myopathies. Practical Neurology. 2019 Jul/Aug:44-53. www.practicalneurology.com. Accessed 22 May 2026; 7. Greenberg SA. Nat Rev Rheumatol. 2019:15(5):257–272; 8. Miernik S, et al. Biomedicines. 2024;12(5):987; 9. Pasnoor M, et al. Neural Clin. 2014;32(3):647–670: 10. Narayanappa G and Nandeesh BN. Brain Pathol. 2021;31(3):el2950.