Polymyositis
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| Polymyositis | |
| Classification and external resources | |
| ICD-10 | M33.2 |
|---|---|
| ICD-9 | 710.4 |
| DiseasesDB | 10343 |
| MedlinePlus | 000428 |
| eMedicine | med/3441 emerg/474 |
| MeSH | D017285 |
Polymyositis is a type of chronic[1] inflammatory myopathy, related to dermatomyositis and inclusion body myositis. Polymyositis means 'many muscle inflammation'.
Contents[hide] |
[edit]Presentation
Polymyositis tends to become evident in adulthood, presenting with bilateral proximal muscle weakness, often noted in the upper legs due to early fatigue while walking. Sometimes the weakness presents itself by the person being unable to rise from a seated position without help, or inability to raise their arms above their head. The weakness is generally progressive, accompanied by lymphocytic inflammation (mainly cytotoxic T8 lymphocytes).
Polymyositis, like dermatomyositis, strikes females with greater frequency than males. The skin involvement of dermatomyositis is absent in polymyositis.
[edit]Causes
The cause is unknown, but seems to be related to autoimmune factors,[2] genetics, and perhaps viruses. In rare cases, the cause is known to be infectious, associated with the pathogensthat cause Lyme disease, toxoplasmosis, and others.
It is hypothesized that an initial injury causes release of muscle auto antigen which is subsequently taken up by macrophages and presented to CD4+ TH cells. Activated TH cells synthesize IFN-γ that stimulate further macrophages and further inflammatory mediator release like IL-1 and TNF-α
Another important event in the Pathogenesis of Polymyositis is increased expression of MHC proteins by m/s cells. Auto-Ag is presented in association with MHC-I molecules on the surface of Myocytes and is recognized by CD8 cytotoxic T cells that subsequently initiate m/s destruction.[citation needed]
[edit]Diagnosis
Diagnosis is fourfold, including elevation of creatine kinase, history and physical examination, electromyograph (EMG) alteration, and a positive muscle biopsy.
Sporadic inclusion body myositis (sIBM): IBM is often confused with (misdiagnosed as) polymyositis and dermatomyositis that does not respond to treatment is likely IBM. sIBM comes on over months to years, polymyositis comes on over weeks to months. It appears that sIBM and polymyositis share some common features, especially the initial sequence of immune system activation, however, polymyositis does not display the subsequent muscle degeneration and protein abnormalities as seen in IBM. As well, polymyositis tends to respond well to treatments, IBM does not. IBM and polymyositis apparently involve different disease mechanisms than are seen in dermatomyositis.
[edit]Symptoms
Marked weakness and/or loss of muscle mass in the proximal musculature, particularly in the shoulder and pelvic girdle. The hip extensors are often severely affected, leading to particular difficulty in ascending stairs and rising from a seated position. Thickening of the skin on the fingers and hands (sclerodactyly) is a frequent feature, although it is non-specific and occurs in other autoimmune disorders of the connective tissues. Dysphagia (difficulty swallowing) and/or other aspects of oesophageal dysmotility occur in as much as 1/3 of patients. Low grade fever and peripheral adenopathy may be present.
[edit]Laboratory Findings
Presence of Anti Jo antibodies in >65% of patients.
[edit]Treatment
Typically, high-dose steroids are employed. Generally, muscle strength will improve within 4-6 weeks (useful to distinguish from inclusion body myositis). Unresponsive patients may be tried on an immunosuppressive medication. IVIG has also shown to be a beneficial treatment.
[edit]References
[edit]External links
- The Myositis Association [1]
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The particular Inclusion Body Myositis Treatment recommended by your expert will rely on the seriousness and kind of issues the nearness of other medical conditions and antagonistic responses to previous treatment.
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