Polymyositis

Definition/Description [edit | edit source]

Polymyositis (PM), a rarest form of myositis with an estimated incidence of approximately 5% of all cases[1] is a chronic inflammatory myopathy [1] [2]which is classified as a persistent inflammatory muscle disease. PM affects striated muscle fibers[1][3], but spares smooth muscle throughout the body[3] and can come on gradually over weeks or months. PM targets proximal musculature,[4] with little to no pain, impairing strength and is characterized by an elevation of serum muscle enzymes and a wide variety of skin abnormalities[2] . 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.  

[5]

Prevalence[edit | edit source]

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.[3] 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.[3] One in 100,000 people have PM with African-Americans more commonly diagnosed than caucasians.

Clinical Presentation[edit | edit source]

The predominant symptom is proximal muscle weakness which is symmetrical[3] [4]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.[4]
Here is a summary of the signs and symptoms

  • Proximal muscle weakness[2] [3]
  • Difficult swallowing (dysphagia)
  • Difficulty swallowing (dysphasia)
  • Difficulty speaking
  • Arthralgia[3][4]
  • Fatigue
  • Shortness of breath[3]


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[6]
  • Variety of cardiovascular complications (i.e. CHF, arrhythmias)[4]
  • Interstitial lung disease[6]


Associated Co-morbidities[edit | edit source]

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

  • Connective tissue diseases: lupus, RA, scleroderma, Sjogrens[2][4]
  • Cardiovascular disease: myocarditis, CHF, heart arrhythmias[2][4]
  • Lung disease[2][6]
  • HIV/AIDS[2]
  • Raynauds Phenomenon[2]
  • Inflamatory bowel disease[7]

Diagnostic Tests[edit | edit source]

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[5]
  • Muscle Biopsy (looking for inflammation, damage, or infection/abdnormal proteins and enzyme deficiencies)[3][4][5]
  • Blood Tests:[4]
    1. Increased Creatine Kinase
    2. Increased Aldolase


Management[edit | edit source]

The management of PM requires multidisciplinary approach which includes Medical management, Physiotherapy and Occupational therapy

Medical Management (current best evidence)6[edit | edit source]


There is no cure for polymyositis however evidence supports that medical management can relieve patient symptoms and give patients more control over their condition. Management of symptoms can allow patients greater function and a better quality of life.[5]

Symptoms vary greatly from patient-to-patient, and all medications have different side effects. Given the difference in presentation of symptoms and individual reactions to medications the course of medical management is unique to each patient. Management may include a combination of pharmacological intervention, physical therapy, and alternative/holistic medicine. Pharmacological management commonly consists of a combination of corticosteroids and immunosuppressants. Corticosteroids are used to reduce inflammation, relieve pain, and improve strength, while immunosuppressants help to dampen the body’s adverse immune response to the patients muscles.


Corticosteroids

Immunosuppressants
• Methotrexate/Azathiprine – often used in combination with prednisone or to allow patients to taper off of Prednisone more quickly. Patients are commonly treated with a combination or Prednisone and Methotrexate from the beginning of their care.
• Cyclophosphamide – more potent than methotrexate and commonly used in patients with disease related lung complications such as interstitial lung disease

Acthar – naturally occurring hormone that is produced in the pituitary gland. Stimulates the release of cortisol from the patient’s adrenal glands, which is a natural alternative to taking corticosteroids. Acthar also reduced the body’s hyperactive immune reponse, thus acting as both a corticosteroid and immunosuppressant. While Acthar would appear to be the ideal pharmacological treatment, there is limited clinical research on its effectiveness. Ongoing studies continue to assess the role of Acthar in the treatment of polymyositis. [4]

Intravenous Immune Globulin (IVIG) – blood product derived from human plasma that actually boosts the body’s immune system response. With immunosuppression being the primary course of medical management it is unclear why some myositis patients benefit from IVIG. IVIG is typically only used in patients who are resistant to other pharmacological treatment. [4][5]

Biologic Agents – Proteins or monoclonal antibodies that inhibit cytokines, which are key players in myositis inflammation.

Anti-TNF Agents – suppress tumor necrosis factor proteins that are associated with inflammation

Rituximab – Targets B cells (lymphocytes) of the immune system, which play a role in the inflammation associated with polymyositis.

Alemtuzumab – Targets T cells (lymphocytes) of the immune system, which play a role in the inflammation associated with polymyositis

Physical Therapy Management[edit | edit source]

Polymyositis and other idiopathic inflammatory myopathies present with wide ranging systemic clinical manifestations. Among those most relevant to physical therapy are muscle weakness, fatigue, and shortness of breath. Musculature proximal to the trunk is the most affected, with marked weakness occurring in the neck, back, shoulders, forearms, thighs, and hips. Distal weakness may occur but is less common however the trunk often remains strong. Respiratory musculature is also usually involved, thus best evidence supports a combination of resistance and aerobic training. The traditional school of thought was that exercise was safe and effective to improve muscle strength and function in patients with chronic, stable polymyositis, but that it may not be appropriate for patients with active, recent onset inflammatory myopathies. More current research has since shown that an exercise program is both safe and beneficial for patients during the recent onset period of the disease. During acute exacerbations it is recommended that patients utilize pharmacological management to control their inflammation prior to starting their exercise program, and limit their physical activity to normal functional mobility. A key goal of physical therapy is to maintain function and reduce fall risk in PM patients. It is important that patients remain active to maintain function, and it is encouraged that they exercise 5-6 times per week. Strengthening exercises should not occur on back-to-back days, however it is recommended that patients practice “active rest days,” where they focus on ROM, positioning, and relaxation rather than strengthening.

Functional Impairments Secondary to Marked Weakness
• Difficulty with all functional mobility (walking, climbing stairs, etc)
• Difficulty lifting, carrying objects
• Difficulty with ADL’s
• Impaired Balance
• Severe Fatigue


Resistance Training
• Preservation of muscle function
• Avoidance of disuse atrophy
• Light resistance (be cautious with eccentric activity)
• Strengthening of distal musculature, which has the greater potential for strength gains, can contribute greatly to an overall improvement in performance with ADL’s
• Open chain exercises utilize less energy than closed chain, but closed chain exercises yield the greatest outcomes with functional mobility.
• Energy conservation is key (avoid high resistance open chain or aggressive closed chain exercises
Aerobic Training
• Cycle ergometer
• Walking

PROM/AAROM/AROM/Stretching
• Contracture prevention

Aquatic Therapy
• Provides ability to mirror functional movements with decreased energy expenditure
• Patient can control resistance of water with modified movement
• Buoyancy assists with posture and lower extremity muscle weakness
• Hydrostatic volume of water increases blood volume in the chest cavity. Patients may experience a significant increase in stroke volume and cardiac output.
• Water turbulence increase blood flow to the surface of the skin
• Therapeutic benefits with a decreased fall risk

Patient education
• A loss of muscle mass results in weakness and fatigue, which may result in the adoption of a sedentary lifestyle. It is very important that patients remain active to avoid disuse atrophy and further muscle weakness.

Differential Diagnosis18[edit | edit source]

Given the intense treatment regimen that is association with autoimmune disorders it is very important that clinicians make an accurate diagnosis in the cases of inflammatory myopathies. Muscle biopsy is essential for an accurate diagnosis, however it is recognized that there is a pathological overlap in different inflammatory myopathies (ex: polymyositis and dermatomyositis) and other muscle disorders such as congenital muscular dystrophies.[4]

Resources[edit | edit source]


The Myositis Association http://www.myositis.org/

American Academy of Neurology http://www.aan.com/

American Autoimmune Related Disease Association http://www.aarda.org/

American College of Rheumatology http://www.rheumatology.org/

Advocating for Chronic Conditions, Entitlements and Social Services (ACCESS) http://www.accredo.com/home.html

John Hopkins Myositis Center http://www.hopkinsmedicine.org/myositis

Myositis Support Group, United Kingdom http://www.myositis.org.uk/

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) http://www.niams.nih.gov/default.asp

National Institute of Neurological Disorders and Stroke (NINDS) http://www.ninds.nih.gov/index.htm

The Muscular Dystrophy Association http://www.mdausa.org/

Polymyositis Clinical Trials
http://www.clinicaltrials.gov/ct/search;jsessionid=D9D2A78BB81C717131DA90D4EDBB3E54?term=polymyositis&submit=Search

References[edit | edit source]

  1. 1.0 1.1 1.2 Sugihara T, Sekine C, Nakae T, Kohyama K, Harigai M, Iwakura Y, Matsumoto Y, Miyasaka N, Kohsaka H. A new murine model to define the critical pathologic and therapeutic mediators of polymyositis. Arthritis & Rheumatism. 2007 Apr;56(4):1304-14.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Schmidt J. Current classification and management of inflammatory myopathies. Journal of neuromuscular diseases. 2018 Jan 1;5(2):109-29.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Hunter K, Lyon MG. Evaluation and management of polymyositis. Indian Journal of Dermatology. 2012 Sep 1;57(5):371.
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 Carstens PO, Schmidt J. Diagnosis, pathogenesis and treatment of myositis: recent advances. Clinical & Experimental Immunology. 2014 Mar;175(3):349-58.
  5. 5.0 5.1 5.2 5.3 5.4 Johns Hopkins Rheumatology. Polymyositis Overview : Johns Hopkins Myositis Center. Available from: http://www.youtube.com/watch?v=aYeH5Y0ozxw [last accessed 30/1/2023]
  6. 6.0 6.1 6.2 Fujisawa T. Management of myositis-associated interstitial lung disease. Medicina. 2021 Apr 3;57(4):347.
  7. Sharif K, Ben-Shabat N, Mahagna M, Shani U, Watad A, Cohen AD, Amital H. Inflammatory Bowel Diseases Are Associated with Polymyositis and Dermatomyositis—A Retrospective Cohort Analysis. Medicina. 2022 Nov 25;58(12):1727.