Researchers at the University of Padova and Spedali Civili di Brescia in Italy conducted a review focused on the role of autoantibodies in myositis and the different clinical phenotypes associated with them. The study was published in the journal Autoimmunity Highlights and is entitled “Myositis autoantibodies and clinical phenotypes.”
Myositis refers to muscle inflammation, and it can be caused by injury, infection, medicines, exercise and chronic diseases. Around 80% of the patients with polymyositis (a condition that leads to progressive muscle weakness) or dermatomyositis (polymyoitis associated to a skin rash) have autoantibodies, making them powerful diagnostic tools.
Myositis autoantibodies can act as proinflammatory and immunostimulating agents in the muscle tissue or far from it, such as in the lung, skin or tumors, suggesting a link between autoimmunity and cancer in myositis.
The myositis autoantibodies are usually classified into two groups depending on their diagnostic accuracy: myositis-specific antibodies (MSA) that are specific for the disease, and myositis-associated antibodies (MAA), which are antibodies that have also been reported in other autoimmune disorders that affect connective tissues such as scleroderma. Examples of MSA are the anti-aminoacyl-tRNA synthetases (ARS) antibodies, anti-SRP antibodies and anti-Mi-2 antibodies. Apart from MSA antibodies, new specific immune targets have been identified such as enzymatic proteins involved in gene expression, namely MDA5, NXP-2, TIF1-gamma, SAE and HMGCR. MAA examples include anti-PM/Scl and anti-Ku.
The team reports that the different MSAs can be associated with distinct clinical polymyositis/dermatomyositis phenotypes as well as disease prognosis. For instance, anti-ARS antibodies are associated with a clinical syndrome characterized by myositis, arthritis and high occurrence of interstitial lung disease, with the joints and lungs being the major organs involved. Anti-Mi-2 antibodies, on the other hand, are linked to skin conditions like dermatomyositis, and they are usually seen as a good prognostic factor due to the associated lower risk of cancer-related myositis.
The research team concluded that MSA can be used as disease serological markers that can help differentiate between distinct subsets of myositis conditions. As these specific autoantibodies play a role in muscle damage, their detection in an early disease stage may help predict the disease course and prognosis.