What is Myositis?

The Idiopathic Inflammatory Myopathies (IIM), which are generally referred to as myositis, is a group of rare, acquired (not inherited), incurable, systemic autoimmune diseases. While myositis is classified as a muscle disease, it can also affect the heart, lungs, skin, and GI tract, and can be associated with cancer. According to the National Organization for Rare Disorders (NORD), the IIMs and subtypes are rare diseases. It is currently estimated that 5-10 people per million are diagnosed with a type of myositis each year. In the U.S., that equates to only 1,600 to 3,200 cases per year. The exact number of myositis cases is difficult to measure, but according to the latest estimate, it was thought, with all forms combined, that there are 50,000 to 75,000 people living with myositis in the U.S.

IIMs are thought to be caused by an overactive immune system that has gone haywire and attacks the body’s own muscles, connective tissue, blood vessels, skin, lungs, and other organs. Idiopathic means the cause is unknown.

The IIMs are highly variable diseases. Two patients with the same diagnosis can present differently, test differently, and respond to available off-label treatments differently.

There are only a couple of FDA approved therapies for any form of myositis.

How does Myositis affect people?

Myositis, such as poly- and dermato-, is a rare, chronic, progressive, inflammatory disease which most often is indicated by symmetrical proximal muscle weakness and skin rashes, and for some, chronic pain. Other symptoms may include fatigue (or asthenia), trouble swallowing, shortness of breath, lung disease, fevers, and weight loss. Patients often have difficulty climbing stairs, rising from a seated position, turning over in bed, raising their arms over their head, and may become prone to falls. Symptoms can appear gradually, over a period of months or even years, or they may develop more rapidly, within days or weeks.

With inclusion body myositis (IBM), the muscle weakness may be asymmetric and involves the distal muscles. The weakness is often slow and progressive. Inclusion body myositis is the most common type of aquired myopathy in patients over the age of 50. First signs may be frequent falls and difficulty with pinching (affects the finger flexors). With IBM, patients are at risk of dysphagia (trouble swallowing) leading to the potential of choking and aspiration pneumonia.

Depending upon the amount of muscle weakness and extent of muscle wasting, some patients may require the use of a cane, walker, wheelchair, power chair, or other assistive devices. 

Adult Dermatomyositis Externally-Led Patient-Focused Drug Development Meeting with the FDA

Poor Long-term clinical outcomes & health-related quality of life in Dermatomyositis & polymyositis

Living with myositis: 

a patient's journey from diagnosis to management

For more information about Myositis