Inflammatory myopathy

Source: Wikipedia, the free encyclopedia.
Inflammatory myopathy
Other namesIdiopathic inflammatory myopathy
Gottron's papules on the hand of a patient with juvenile dermatomyositis.
SpecialtyRheumatology Edit this on Wikidata

Inflammatory myopathy, also known as idiopathic inflammatory myopathy (IIM), is disease featuring muscle weakness, inflammation of muscles (myositis), and in some types, muscle pain. The cause of much inflammatory myopathy is unknown (

immune-mediated necrotising myopathy (IMNM), and focal autoimmune myositis.[1]

Diagnosis

Idiopathic inflammatory myopathy is a

inclusions in both cytoplasm and nucleus.[3]

Treatment

There have been few randomized treatment trials, due to the relative rarity of inflammatory myopathies.[4] The goal of treatment is improvement in activities of daily living and muscle strength. Suppression of immune system activity (immunosuppression) is the treatment strategy. Patients with PM or DM almost always improve to some degree in response to treatment, at least initially, and many recover fully with maintenance therapy. (If there is no initial improvement from treatment of PM or DM, the diagnosis should be carefully re-examined.) There is no proven effective therapy for IBM, and most IBM patients will need assistive devices such as a cane, a walking frame or a wheelchair. The later in life IBM arises, the more aggressive it appears to be.[5]

Polymyositis and dermatomyositis

In severe cases of PM and DM with systemic signs, an initial three to five days on intravenous

cyclosporine, may be used in combination with reduced prednisone. Some of these steroid sparing drugs can take several months to demonstrate an effect.[5]

To minimize side effects, patients on corticosteroids should follow a strict high-protein, low-carbohydrate, low-salt diet; and with long-term corticosteroid use a daily calcium supplement and weekly vitamin D supplement (and a weekly dose of

Fosamax for postmenopausal women) should be considered.[5]

For patients not responding to this approach there is weak evidence supporting the use of intravenous

mycophenolate mofetil and other agents; and trials of rituximab have indicated a potential therapeutic effect.[4]

Inclusion-body myositis

Despite its very similar clinical presentation to PM, IBM does not respond to the drugs that effectively treat PM, and there is no proven effective therapy for IBM.[5] Alemtuzumab is being studied but as of May 2013 it had not demonstrated clinical effectiveness in IBM.[4] Dysphagia (difficulty swallowing) may be improved by intravenous immunoglobulin, though more trials are needed.[6] Non-fatiguing, systematic strength-building exercise has demonstrated benefit.[7] Occupational and rehabilitation therapists can offer good advice on walking without falling and performing fine motor tasks, and can provide appropriate canes, braces and wheelchairs. Speech pathologists can provide advice on preventing choking episodes and reducing the anxiety of an immanent aspiration for both patients and carers.[5]

Epidemiology

Every year between 2.18 and 7.7 people per million receive a diagnosis of PM or DM.[8] Around 3.2 children per million per year are diagnosed with DM (termed juvenile dermatomyositis), with an average age of onset of seven years. Diagnosis of adult DM commonly occurs between 30 and 50 years of age. PM is an adult disease, usually emerging after the age of twenty. PM and DM are more common in females, more common in Caucasians, and least common in Asians. At any given time, about 35.5 people per million have IBM; it emerges after the age of 30 (usually after 50), and may be more common in males.[4]

Differential diagnoses

Myositis (inflammation of the muscle) can be caused secondary to a number of primary diseases including: infection, muscle trauma, medications and toxins, inherited muscle diseases, and autoimmune disease such as lupus. Other autoimmune diseases can mimic the symptoms of IMM (muscle weakness and autoantibodies), including Lambert-Eaton myasthenic syndrome, myasthenia gravis, and the muscle form of sarcoidosis.[1]

Although idiopathic inflammatory myopathy (IIM) is a diagnosis of exclusion, it is often the initial misdiagnosis of several acquired non-inflammatory myopathies.[1][9][10] This is due to a number of factors, including:

  • overlapping symptoms (such as muscle weakness, pain, elevated CK);
  • that delaying treatment for an inflammatory myopathy, in order to exclude potential non-inflammatory myopathies, may cause irreversible damage (although administering immunosuppressants and glucocorticosteroids to non-inflammatory myopathies may also cause damage);
  • that many of the testing methods for idiopathic inflammatory myopathy are non-specific (the same results could apply to many different myopathies);
  • and the unfamiliarity of the many rare diseases that are outside of rheumatology.[1][10]

Acquired non-inflammatory myopathies include toxin-induced myopathies, endocrine myopathies, metabolic myopathies, muscular dystrophies, congenital myasthenic syndrome, nutritional imbalances, and infection.[11][1]

See also

References

  1. ^
    PMID 30505013
    .
  2. ISBN 9781627038393
    .
  3. ISBN 9781627038393
    .
  4. ^
    ISBN 978-1-118-63549-0
    .
  5. ^
    ISBN 9781437703726
    .
  6. ISBN 9781437703726
    :
  7. PMID 9324080
    . Cited in:
  8. S2CID 24978554
    . Cited in:
  9. S2CID 25515951
    .
  10. ^
    S2CID 250012951
    .
  11. PMID 23597974
    .

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Inflammatory_myopathy&oldid=1210920689"