What is Overlap Myositis?

Overlap Myositis (OM) may occur when a person has the signs and symptoms of Myositis with those of another systemic rheumatic disease such as:

Research suggests that the signs and symptoms of systemic sclerosis (SSc, scleroderma) may be the most prevalent occurring in Overlap Myositis. Rheumatoid arthritis and Sjögren’s syndrome appear to occur less often in Overlap Myositis. OM appears to be more common in adult women.

However, it is important to note that the precise diagnostic criteria of OM are still under scientific debate.

Signs and Symptoms

The signs and symptoms of Overlap Myositis can include those of Myositis combined with one or more of a systemic rhematic disease such as:

While further studies are required, initial research suggests that the prime distinguishing features of OM may include:

  • Raynaud’s phenomenon ­– temporary disruption of blood flow to the small blood vessels in extremities. In response to cold or stress, your fingers, toes, tip of the nose, lips and ears can turn blue, feel cold and numb. After the blood flow returns, you may feel tingling and throbbing in the affected areas.

  • Sclerodactyly ­– tightness and thickening of skin on fingers and toes. It may make fingers harder to bend. 

What causes Overlap Myositis?

The cause of Overlap Myositis is not fully understood. For more information, click the links above for each overlapping disease type in ‘Signs and Symptoms’.

How is Overlap Myositis diagnosed?

The precise diagnostic criteria of OM are still under scientific debate. Screening for Myositis-specific and Myositis-Associated autoantibodies may improve diagnosis.

How is Overlap Myositis treated?

Treatment depends on the type of overlap signs and symptoms that you have. Usually, treatment is based on the use of corticosteroids and/or other immunosuppressants.

For those who have Myositis overlapping systemic sclerosis (SSc, scleroderma), treatment with high-dose steroids should generally be avoided because of the high risk of kidney crisis.

What research is being done?

Research is ongoing to learn more about Overlap Myositis and test potential treatments.


Abatacept is a modified antibody designed to reduce inflammation by interfering with and reducing the activity of immune cells in our body, called T-cells. It is currently used as an effective treatment for many people living with arthritis.

A phase 3, randomized, double-blind clinical trial to evaluate the efficacy and safety of abatacept in adults with OM, PM, DM, Autoimmune Necrotizing Myopathies and JM is currently underway. The estimated study completion date is October 2024.

Stay up to date

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