Polymyositis

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Original Editors - Chris Pyles & Kayla Thiesen from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description^1,2

Polymyositis (PM) is a chronic inflammatory myopathy, which is classified as a persistence inflammatory muscle disease. PM affects striated muscle fibers, but spares smooth muscle throughout the body and can come on gradually over weeks or months. PM targets proximal musculature, with little to no pain, impairing strength and is characterized by an elevation of serum muscle enzymes and a wide variety of skin abnormalities, sometimes including cardiopulmonary impairments. Although no pain is present, some tenderness may occur directly over involved musculature, but all deep tendon reflexes are preserved. The general approach to treating polymyositis is through pharmacological and conservative treatment to increase strength and prevent development of extra-muscular disease in order to better outcomes for the patient.

Prevalence²

Current literature is unclear about the age of presentation – some articles state it mostly affects adults in their 30’s to 50’s, while other sources say the onset is in adults aged 50-70. Although research shows that it is rare to have an onset earlier than 18 years of age, it has been proven that females are more susceptible to PM than males with a ratio of 2:1. One in 100,000 people have PM with blacks more commonly diagnosed than whites.

Characteristics/Clinical Presentation^1,2

Symptoms are symmetrical and can gradually appear or may fluctuate within short or long periods of time. Functionally, patients may have issues with grabbing a glass off of a high shelf, climbing stairs, or getting up or sitting down on a couch.

With progression of the disease, neck and shoulder girdle musculature can be involved resulting in minimal muscle contraction or paralysis.

Here is a summary of the signs and symptoms

• Proximal muscle weakness
• Difficult swallowing (dysphagia)
• Difficulty speaking
•  Mild joint or muscle tenderness
• Fatigue
• Arthralagia
• Shortness of breathe
• Malnutrition
• Weight loss
• Calcium deposits
• Morning stiffness

As PM progresses, it can affect the upper esophagus as well as striated muscle fibers in the chest wall. As a result, patients can have more complex signs and symptoms such as:

• Aspiration pneumonia
• Respiratory failure
• Variety of cardiovascular complications (i.e. CHF, arrhythmias)
• Interstitial lung disease
  
  

Associated Co-morbidities^1,2,3,4

Since Polymyositis is a autoimmune disease, it is often associated with other autoimmune dieases and infectious disorders:

• Connective tissue diseases: lupus, RA, scleroderma, Sjogrens
• Cardiovascular disease: myocarditis, CHF, heart arrhythmias
• Lung disease
• HIV/AIDS
• Raynauds Phenomenon
  

Medications¹

Earlier treatment is always better – your doctor will decide based on your symptoms what treatment will be more tailored to you. There have not been very many scientific studies which effects insurance coverage and you should be closely monitored for adverse side effects:

• Corticosteroids
• Immunosupressive therapies (If cortico-steroids aren’t working)
  1. Corticosteroid sparing agents (Azasan, Imuran, Trexall, Methotrexate, Rheumatrex).
  2. Intravenous immunoglobulin (IVIG).
  3. Tacrolimus (Prograf)
  4. Cyclophosphamide (Cytoxan)
  5. Cyclosporine (Gengraf, Neoral, Sandimmune)
• Biological therapies (Severe Cases, only if the above two didn’t work)
  1. Rituximab (Rituxan)
  2. Tumor necrosis factor (TNF) inhibitors (Enbrel, Remicade)

Diagnostic Tests/Lab Tests/Lab Values¹

There are several different diagnostic tools to determine if a patient has polymyositis, it can be a long process and both health care providers as well as patients are encouraged to remain patient:

• Magnetic Resonance imaging (MRI)
• Electromyography
• Muscle Biopsy (looking for inflammation, damage, or infection/abdnormal proteins and enzyme deficiencies)
• Blood Tests:
  1. Increased Creatine Kinase
  2. Increased Aldolase
  
  

Etiology/Causes^1,5

The cause is officially unknown, but it has been shown to be related to other autoimmune diseases with detectable level of autoantibodies in their blood, genetics, and some undisclosed viruses. (1)

Systemic Involvement

Musculoskeletal

• Proximal muscle weakness resulting in a decrease in functional mobility (Neck, back, shoulders, forearms, hips, and thighs)
  
• Involvement of pharyngeal and esophageal muscles may impair swallowing, leaving patients at risk for aspiration
  
• Patients are at an increased risk to develop contractures
  
• Joint manifestations tend to be mild (approximately 30% of patients may experience polyarthralgia or polyarthritis (joint pain or arthritic manifestations in multiple joints)
  
  

Cardiopulmonary

• Dyspnea
• Cough
  
• Cardiac arrhythmias can occur but are often asymptomatic
  

Gastrointestinal

• More common manifestation in children
  
• Hematemesis (vomiting of blood)
  
• Melena (black, tarry feces)
  
• Ischemic bowel perforation
  
  

Medical Management (current best evidence)

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Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)

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Differential Diagnosis

These include nerve-muscle diseases (such as muscular dystrophies), drug toxins (such as alcohol, cocaine, steroids, colchicine, hydroxychloroquine, and cholesterol-lowering drugs, called statins), metabolic disorders (where muscle cells are unable to process chemicals normally), hormone disorders (such as abnormal thyroid), calcium and magnesium conditions, and infectious diseases (such as influenza virus, AIDS, streptococcus and Lyme bacteria, pork tapeworm and schistosomiasis). (5)

Case Reports/ Case Studies

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Resources

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Recent Related Research (from Pubmed)

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References

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1. Mayo Foundation for Medical Education and Research (MFMER). Polymyositis. http://www.mayoclinic.com/health/polymyositis/DS00334/DSECTION=symptoms. July 2011. April 2013.
2. Hunter K, Lyon M. Evaluation and Management of Polymyositis. Indian Journal of Dermatology. 2012; 57(5):371-374
3. Pheonix Neurological Associates. Polymyositis. http://www.phoenixneurology.com/specialties/polymyositis.php. 2011. April 2013
4. National Institute of Neurological Disorders and Stroke. Polymyositis Information Page. http://www.ninds.nih.gov/disorders/polymyositis/polymyositis.htm. 2011. April 2013.
5. Sheil, W. Polymyositis and Dermatomyositis. http://www.medicinenet.com/polymyositis/article.htm#what_causes_polymyositis. 2012. April 2013.