By Dr Naresh Purohit 

(Executive Member- Indian Rheumatology Association)

Myositis is an autoimmune condition in which the immune system itself attacks the muscles of the body.The prevalence of this condition is between 4-22 cases per one lakh population, according to the Indian Journal of Rheumatology.

The prevalence of Idiopathic Infective Myopathies is 9--14 cases per 100,000 individuals in India. Patients present with muscle weakness and extramuscular manifestations involving the lung, heart, skin, and musculoskeletal systems. Some patients have no obvious clinical muscle weakness but skin lesions alone. Medics since 1916 have known that patients with myositis were at high risk of cancer. Recent research  studies have quantified the risk, finding that dermatomyositis patients face a threefold risk of cancer, while patients with polymyositis face a 40 percent increase in risk. 

It  is to be noted that cancer and myositis often appear around the same time. The cancer is usually diagnosed within a year of the muscle disease; while both may go into remission after treatment, the recurrence of one often augurs the recurrence of the other.

There are different types of Myositis — Polymyositis and Dermatomyositis are the most common ones.

The common age group to experience myositis is 40-50 years. A person affected by this condition may not be able to walk due to the pain in the muscles.

General myositis affects the skeletal muscles, the ones which move arms and legs. Smooth muscles, the ones which are present in the intestine or lungs are not generally affected but can get involved in special cases. Myositis can also affect cardiac muscles that may lead to a drastic and dreaded complication causing a life threatening issue. 

Since the muscles which act around  shoulders and hip region might be affected, the person may not be able to walk or climb the stairs or reach an object above their head or lift an object.

Umpteen research studies across the globe have shown myositis to be a genetic disease. Data show that having at least one first-degree relative with myositis is strongly associated with the risk of it and that several human leukocyte antigen (HLA) regions are associated with it.

Myositis is a treatable disease and can be cured with proper medical attention provided diagnosed early.

A person suffering from this disease will have to be on medications for a long time to prevent this from relapsing. Steroids, oral or intravenous and immunosuppression therapy with drugs like methotrexate and azathioprine can help treat this illness.

Sometimes the patient may require high doses of intravenous steroids to halt the progression of illness faster. In resistant cases doctors use plasma exchange on dialysis machines, intravenous immunoglobulin and rituximab.

In some cases, the immune cells bite away the muscles so much that the muscle breaks down. Those waste products of the muscle breakdown and get stuck in the kidneys which can lead to certain complications like the urine becoming dark brown in colour.