DO YOU KNOW YOUR ANTIBODY?

Many people don’t know what type of antibody they have. In a survey conducted by Know Rare through social media, we found that only 2 out of 15 people, who said they had myositis, knew what antibody they had. Many people did not know what type of myositis they had, unless it was dermatomyositis and they had a rash. Very few of the survey responders had ever heard of the diagnosis of Immune-mediated necrotizing myopathy (IMNM). When we followed up on the survey by asking a few myositis specialists in the US and in Europe how they describe the diagnosis to patients, the most common ways they explained it was “myositis” or “autoimmune myositis.”

ANTIBODIES ASSOCIATED WITH A MYOSITIS DIAGNOSIS

It is estimated that 45-85% of people with myositis have tested positive for myositis-specific (MSA)  (depending on the accuracy of the test).

Diagnosis is not solely made from an antibody test, but in necrotizing myopathies, there are two different antibodies, the anti-HMGCR and the anti-SRP, and the disease experience can be different, depending on which antibody you have. The anti-HMGCR antibody seems to be more associated with people who have been taking statins. People with the anti-SRP antibody tend to have more severe disease, with significant muscle weakness.

Those who test positive for the anti-synthetase antibody may be more likely to have some type of lung complications and Raynaud’s. (a condition that causes some areas of the body — such as fingers and toes — to feel numb and cold in cold temperatures or when under stress)

WHAT MEASURES OR WAYS DO DOCTORS KNOW IF MYOSITIS TREATMENT IS WORKING?

Specialists’ approach to the treatment of myositis is individualized, taking into account the type of myositis, the degree of muscle weakness, age, how long since diagnosis, other conditions you might have, and other symptoms that affect skin and/or lungs. Though the treatment most prescribed for all myositis (except IBM) are glucocorticoids (a type of corticosteroids that reduces inflammation) along with immune modulators such as methotrexate, azathioprine, mycophenolate, and rituximab, people with dermatomyositis may also be treated with anti-malarial drugs. For many, intravenous infusions with immunoglobulin (IVIg) are used to get a quick response.

Doctors may monitor the level of a muscle enzyme, creatinine kinase (CK) to see how well the treatment is reducing a high level. In some cases of polymyositis, the CK levels may be 50 times the normal rate, and the treatment’s aim is to reduce it. The CK levels are a signal of the disease’s activity against the muscles, so if the numbers go down after treatment, it’s a sign the treatment may be working.