What is Polymyositis?
It is a disease characterized by the persistent inflammation of the skeletal muscles. It belongs to a group of disorders known as myositis and is related to inclusion body myositis and dermatomyositis. This relatively uncommon condition is medically categorized as chronic inflammatory myopathy that leads to weakness, swelling, tenderness and damage of muscles.
The condition is noticed in both children and adults. Apart from humans, it is also known to affect dogs.
The exact factors responsible for Polymyositis are not known. However, the involvement of certain autoimmune factors and viruses is suspected. Polymyositis and dermatomyositis may be triggered by cancer; an immune response against cancer may prove to be detrimental to some muscle components.
Polymyositis is believed to be caused by some infectious agents in some rare instances. The pathogens responsible for Lyme disease and toxoplasmosis as well as some other health conditions may play an important role in the development of this disorder. The condition is generally considered to be non-fatal in the absence of interstitial lung disease.
Doctors hypothesize that some initial injury may release muscle auto-antigen that is eventually taken up by the macrophages and then presented to the CD4+ T Helper cells. The activated T Helper cells synthesize IFN-γ which leads to further stimulation of the macrophages and further release of inflammatory mediators like TNF-α and IL-1.
The immune system of a healthy individual protects the healthy cells from being attacked by foreign substances like viruses and bacteria. In Polymyositis patients, an unknown cause might send a signal to the immune system to produce autoimmune antibodies that attacks the own tissues of the body. Due to this, many individuals having Polymyositis show a significantly high level of autoimmune antibodies in their blood.
This is a systemic disorder that affects the entire body. Its various symptoms include:
- Joint pains
- Weight loss
- Morning stiffness
- Reduced appetite
- Shortness of breath
- Esophageal dysmotility
- Peripheral adenopathy
- A propensity to fall
- Muscle tenderness and pain
- Difficulty in swallowing or dysphagia
- Wide-footed posture and walking style
- Sclerodactyly (a frequent non-specific symptom)
- Weakness of the throat muscles causing changes or other problems with voice
- Foot drop in either or both feet, which might indicate advanced polymyositis as well as IBM (Inclusion Body Myositis).
- Reduced muscle mass and marked weakness in proximal musculature, especially in the pelvic girdle and shoulder which causes difficulty in lifting the arms over the head, climbing stairs or standing upright from the seated position.
Polymyositis is also linked with an increased occurrence of some types of cancer, especially bladder and lung cancers as well as Non-Hodgkin lymphoma. Weakness experienced due to the disorder is usually progressive and is accompanied by lymphocytic inflammations.
Diagnosing Polymyositis is a difficult process as the signs and symptoms of this condition often overlap with certain other diseases and related conditions. In the initial stages, a doctor usually conducts a thorough medical checkup of the different parts of the body. He might then recommend various blood tests, imaging tests or electrical tests to conclusively prove the presence of polymyositis in a patient.
The various blood tests carried out for diagnosing this condition include:
- Serum aldolase
- Creatine kinase (CK)
- Anti-SRP antibodies
- Muscle enzyme tests
- Lactate dehydrogenase (LDH)
- Creatinine phosphokinase or CPK
- Serum glutamic pyruvic transaminase (SGPT) test
- Serum glutamic oxaloacetic transaminase (SGOT) test
- Tests for checking the presence of autoimmune antibodies
People having anti-SRP antibodies are affected by acute polymyositis. They also exhibit cardiac problems, respond poorly to therapy and have a poor outcome.
The imaging tests conducted for evaluating polymyositis include MRI scans and chest X-rays.
A nerve conduction velocity test and electromyography (EMG) examination are electrical tests that allow detection of any muscle abnormalities that are typical of Polymyositis and exclude other nerve-muscle disorders.
Other diagnostic procedures
Other diagnostic and screening tests associated with this condition include:
- PAP smears
- Urine tests to evaluate the presence of myoglobin
- Tests to detect signs of bacterial and/or parasitical infections
- Muscle biopsies to see signs of inflammations, necrosis as well as degeneration and restoration of the muscle fibers
Polymyositis Differential Diagnosis
There are numerous health conditions that show signs and symptoms similar to that of Polymyositis, making it difficult to reach a conclusive diagnosis. However, it is important to distinguish Polymyositis from such similar conditions in order to decide on the appropriate treatment methods. The differential diagnosis for this condition includes:
- Focal myositis
- Myasthenia gravis
- Giant cell myositis
- Myositis ossificans
- Cushing Syndrome
- Muscular dystrophy
- Metabolic myopathy
- Eosinophilic myositis
- Rheumatoid Arthritis
- Inclusion body myositis
- Polymyalgia Rheumatica
- Diabetic polyradiculopathy
- Systemic Lupus Erythematosus
- Overlapping connective tissue disorders
The primary curative method for Polymyositis involves usage of corticosteroids. High doses of Prednisone are often successful in dramatically improving the health of sufferers. These medications help in reducing inflammations and activities of the immune system. Doctors may also recommend maintenance therapy involving Prednisone for an indefinite period of time. Immunosuppressive medications such as azathioprine and methotrexate may be administered to patients who are unresponsive to corticosteroid treatment.
Another effective way of treating this condition is by using intravenous immunoglobulin (IVIG). It is a special protein that is obtained from the plasma of blood donors. This method has shown good results in curing many difficult cases.
Certain investigational medications might help in improving the health of patients in some severe cases. These include tumor necrosis factor inhibitors and Rituximab.
Sometimes, surgery is required to cure Polymyositis. If a tumor is associated with the condition, a surgical procedure to remove the tumor can improve the health of affected individuals.
Plasmapheresis is a treatment method that involves removal of antibodies from the bloodstream which are responsible for attacking the muscle tissues. Blood is obtained from patients and blood cells are then separated from plasma. The antibodies are left over in the plasma and only the purified blood cells are then returned to the patients.
Specialized physical exercises are also used to supplement medical treatments as these help to strengthen the muscles and improve the overall quality of life. Chewing or swallowing can prove to be a challenge for the later stage Polymyositis patients. A dietician can teach sufferers to prepare foods that are easy to ingest. Speech therapy is useful for people who are experiencing speech problems due to this disorder.
A number of complications can result from severe cases of Polymyositis. These include:
- Heart disorders
- Cancerous conditions
- Aspiration pneumonia
- Abdominal complications
- Side effects from corticosteroid medications
- Breathing problems, such as respiratory failure
- Difficulty in swallowing, which might lead to malnutrition
- Calcinosis or accumulation of calcium in affected muscles, skin as well as connective tissues
The outcome for this condition varies and can be influenced by the presence of complications. The five-year mortality rate can be around 20%. Several patients, especially children, can enter an asymptomatic phase (remission) and recover. Most other people respond positively to treatment by immunosuppressant drugs. Associated problems that affect patients for a long time, and even result in deaths of adult sufferers, mainly include:
- Respiratory failure
- Malignant cancers
- Lung diseases
- Severe muscle weakness
Polymyositis Support Groups
There are a number of support groups that provide medical assistance to the families affected by this condition, increase awareness as well as act as a platform for people from various backgrounds to connect with each other.
Here are some images that display the condition of the muscle tissues affected by this disorder.
Picture 1 – Polymyositis
Picture 2 – Polymyositis Image
Polymyositis is an inflammatory muscle condition that affects both children and adults. It results in progressive degeneration of the muscles and leads to general weakness as well as other severe symptoms. Early diagnosis and proper treatment can ensure survival and good health of patients. Without proper curative options, this disorder can give rise to fatal consequences.