Myositis

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton  

Introduction

Myositis is a group of rare conditions where the body’s immune system turns against itself and destroys healthy muscle tissue instead of building new muscle tissue. Myositis is also known as idiopathic inflammatory myopathy(IIMs).

• This set of acquired diseases affect the muscle but may additionally affect other organs.
• Timely diagnosis and treatment leads to better outcomes, less permanent damage, and less long-term disability.
• Myositis mainly occur in middle-aged patients, most showing a subacute weakness and myalgia in the upper and lower limbs and extramuscular manifestations..

Sub-Types

Include these types:

• Necrotizing autoimmune myositis is rare and likely associated with connective tissue disorders, cancer, and drugs, for example, statins. Distinguished by acute or subacute muscle weakness and myocyte necrosis (lacking inflammation on histopathology). Occurs months to even years after statin use.
• Dermatomyositis, which can affect the muscle and presents with a typical skin rash.
• Inclusion body myositis, with a purely muscular expression and leads to a slow progressive deficit
• Immune-mediated necrotizing myopathies, with a severe muscle involvement often presents from the onset of the disease
• Antisynthetase syndrome (ASS), which combines muscle damage, joint involvement and a potentially life-threatening lung disease
• Overlapping myositis, which combines muscle damage with other organs involvement connected to another autoimmune disease.

Diagnosis of Myositis

Diagnosis is based on diligent clinical examination, electromyographic studies and immunological testing for myositis specific antibodies. Muscle biopsy is no longer routinely recommended when the antibodies are typical, unless the form of IIM issometimes difficult to classify.

Course of IIMs

Infections, drugs, rheumatologic diseases, and malignancies are all potential causes of myositis and are important to diagnose as they may have distinct therapies beyond immunomodulatory therapy.

IMMs are progressive, however relapsing and remitting with periods of worsening and quiescence can occur. The disease course is varies being either: monophasic, meaning the patient can eventually be tapered off medication; chronic, requiring medication; or polyphasic, with the patient experiences relapse and remission. The typical course of myositis begins with weakness over days to weeks, or it can present more slowly over a few months. The proximal arms and legs are usually affected along with the neck flexors. In roughly 1/3 of individuals, weakness of oropharyngeal and esophageal muscles results in dysphagia. When muscle inflammation leads to irreversible muscle atrophy and fatty replacement (as in some cases), permanent muscle weakness in these muscle groups persists because of permanent damage.

Treatment

Main goals of IIM therapy

• Restore muscle strength
• Limit/eliminate the inflammation
• Prevent other organs damage.

Ideally the treatment should involved a multidisciplinary approach with input from neurology, rheumatology, dermatology, pulmonary, physical therapy, occupational therapy, and speech therapy.

Treatment includes high-dose glucocorticoids, steroid-sparing agents, and intravenous immunoglobulins (IVIG).

To date scores immunosuppressive and immunomodulatory therapeutic agents are available for the treatment of myositis. Glucocorticosteroids (GC) and immunosuppressants remain first-line therapy in many cases with early start and sufficient dosing potentially leading to stabilization of the disease, improvement of strength and decrease in inflammation. Unfortunately the side effects of immunosuppressive treatment may be undesirable. New therapeutic approaches targeting specific immunological pathways are show great promise.

GC therapy can cause many adverse effects, including muscle and bone loss, weight gain and build up of visceral fat, lipid and glucose impairment, and fluid and electrolyte imbalances. Nutritional strategies should aim to ensure adequate intake of high-quality protein, ensure calcium and vitamin D levels are maintained, and having a diet on unprocessed or minimally processed food sources, and minimizing ultra-processed food intake.

Until now there was little understanding of the pathogenesis of IMMs. Today this is changing with understanding of idiopathic inflammatory myopathies evolving. In the past decade, improved diagnostic tools have facilitated an enhanced understanding of the underlying disease mechanisms in idiopathic inflammatory myopathies, enabling the expansion of therapeutic trials. Great optimism exists now in this area, with progress in innovative diagnostics, outcome measures, and therapeutic approaches occurring.

Physiotherapy

Exercise therapy leads to a stabilization of disease progression, with evidence in the literature supporting moderate physical exercise in patients with myositis.

• Research has shown that an exercise programs at home improve muscle strength and endurance.
• Concentric sport activities are appropriate as they cause less injury to muscle fibers than eccentric exercise. Stretching that happens in eccentric sport exercise may cause myalgia, elevated inflammatory response, and an increase of Creatine kinase (CK). CK is an enzyme present in skeletal muscle, heart muscle and brain. When any of these tissues are damaged CK gets into the bloodstream. raised CK levels may indicate muscle injury or disease.
• Aerobic training, for example cycling and resistance exercise over 12 weeks, three times per week, results in an improvement in muscle strength, and does not lead to a significant rise in CK levels post training. The evidence in the literature clearly supports moderate physical exercise in patients with myositis.

See also this page for more Inflammatory Myopathies

Resources

This video made by the The Myositis Association is one of several this site has and is very useful for physiotherapists to watch.