{{short description|Inflammation of skeletal muscle}} {{for multi|the "forget-me-not" plant|Myosotis|the phase of cell division|Mitosis|the "mouse-eared bats"|Myotis}} {{Infobox medical condition (new) | name = Myositis | synonyms =
| image = IBM rimmed vacuoles HE x200.jpg | caption = A muscle biopsy from someone who is diagnosed with{{clarify|date=July 2024}}{{explain|date=July 2024|reason=what in the picture shows that, what is what?}} myositis. | pronounce = | field = Rheumatology | symptoms = | complications = Amplified musculoskeletal pain syndrome<ref name=ChildrensHealth>{{cite web |url=https://www.childrens.com/specialties-services/conditions/amplified-musculoskeletal-pain-syndrome-amps |title=Amplified Musculoskeletal Pain Syndrome (AMPS) |publisher=Children's Health}}</ref> | onset = | duration = | types = | causes = Autoimmunity, idiopathic, adverse drug reaction | risks = | diagnosis = | differential = | prevention = | treatment = | medication = | prognosis = | frequency = | deaths = }}
'''Myositis''' is a rarely encountered medical condition characterized by inflammation affecting the muscles.<ref name="Carstens_2014">{{cite journal |vauthors=Carstens PO, Schmidt J |date=March 2014 |title=Diagnosis, pathogenesis and treatment of myositis: recent advances |journal=Clinical and Experimental Immunology |volume=175 |issue=3 |pages=349–358 |doi=10.1111/cei.12194 |pmc=3927896 |pmid=23981102}}</ref> The manifestations of this condition may include skin issues, muscle weakness, and the potential involvement of other organs.<ref name="Betteridge_2016">{{cite journal |vauthors=Betteridge Z, McHugh N |date=July 2016 |title=Myositis-specific autoantibodies: an important tool to support diagnosis of myositis |journal=Journal of Internal Medicine |volume=280 |issue=1 |pages=8–23 |doi=10.1111/joim.12451 |pmid=26602539 |s2cid=41157692 |doi-access=free}}</ref> Additionally, systemic symptoms like weight loss, fatigue, and low-grade fever can manifest in individuals with myositis.
==Causes== Myositis can arise from various causes, including injury, certain medications, infections, inherited muscle disorders, or autoimmune conditions. In some instances, the origins of myositis remain idiopathic, without a discernible cause. * Injury: A mild form of myositis can occur with hard exercise.<ref name="Hoffman_2021">{{Cite web | vauthors = Hoffman M | veditors = DerSarkissian C | date = 19 April 2021 |title=Myositis: Symptoms and Causes |url=https://www.webmd.com/a-to-z-guides/myositis-symptoms-treatments-prognosis |access-date=2022-06-12 |website=WebMD |language=en}}</ref> A more severe form of muscle injury, called rhabdomyolysis, is also associated with myositis.<ref name="Hoffman_2021" /> This is a condition where an injury to the patient's muscles causes them to quickly break down.<ref name="Hoffman_2021" /> * Medicines: A variety of different medicines can cause myositis. One of the most common types of drugs that can cause myositis are statins, which are used to lower cholesterol levels. One of the most common side effects of statin therapy is muscle pain<ref name="Sathasivam_2008">{{cite journal | vauthors = Sathasivam S, Lecky B | title = Statin induced myopathy | journal = BMJ | volume = 337 | article-number = a2286 | date = November 2008 | pmid = 18988647 | doi = 10.1136/bmj.a2286 | s2cid = 3239804 }}</ref> which, more rarely, can lead to myositis.<ref name="Sathasivam_2008" /> * Infection: The most common infectious cause of myositis is viral infections, such as the common cold.<ref name="Hoffman_2021" /> Other viruses, such as COVID-19, are also shown to be a rare cause of myositis.<ref>{{cite journal | vauthors = Saud A, Naveen R, Aggarwal R, Gupta L | title = COVID-19 and Myositis: What We Know So Far | journal = Current Rheumatology Reports | volume = 23 | issue = 8 | page = 63 | date = July 2021 | pmid = 34216297 | pmc = 8254439 | doi = 10.1007/s11926-021-01023-9 }}</ref> Benign acute childhood myositis has been described in children after prodromal viral infections with different viral agents. Bacterial, parasitic, and fungal infections are other infectious causes of myositis.<ref>{{cite journal | vauthors = Szczęsny P, Świerkocka K, Olesińska M | title = Differential diagnosis of idiopathic inflammatory myopathies in adults - the first step when approaching a patient with muscle weakness | journal = Reumatologia | volume = 56 | issue = 5 | pages = 307–315 | date = 2018 | pmid = 30505013 | pmc = 6263305 | doi = 10.5114/reum.2018.79502 }}</ref> * Inherited muscle disease: Many inherited myopathies may have secondary myositis, including calpainopathy, dysferlinopathy, facioscapulohumeral muscular dystrophy, dystrophinopathy, and ''LMNA''-associated myopathy.<ref>{{cite journal | vauthors = Tarnopolsky MA, Hatcher E, Shupak R | title = Genetic Myopathies Initially Diagnosed and Treated as Inflammatory Myopathy | journal = The Canadian Journal of Neurological Sciences. Le Journal Canadien des Sciences Neurologiques | volume = 43 | issue = 3 | pages = 381–384 | date = May 2016 | pmid = 26911292 | doi = 10.1017/cjn.2015.386 | s2cid = 25515951 | doi-access = free }}</ref> * Autoimmune: Autoimmune disease is an abnormal immune response to specific body protein or other biomolecular target, such as one of the muscles. The three main types of idiopathic myositis (known as inflammatory myopathies) that typically test positive for autoantibodies are dermatomyositis, polymyositis, and inclusion body myositis.<ref name="Hoffman_2021" /> Other autoimmune diseases, such as systemic lupus erythematosus, can also cause myositis-like symptoms.<ref name="Hoffman_2021" />
==Diagnosis== There are various tools that can be used to help diagnose myositis. The most common methods are physical examination, electromyography (EMG), magnetic resonance imaging (MRI), muscle biopsy, and blood tests. The first course of action a doctor will likely take is perform a physical exam.<ref name="Carstens_2014" /> The doctor assesses for muscle weakness or rashes.
Another possible test is electromyography. This test involves the insertion of small needles into the patient's muscles.<ref name="Hoffman_2021" /> This allows a physician to look at the muscles' responses to various electrical nerve stimuli and evaluate which muscles potentially have myositis.<ref name="Hoffman_2021" /> Magnetic resonance imaging can be useful in diagnosis,<ref>{{cite journal | vauthors = Pipitone N | title = Value of MRI in diagnostics and evaluation of myositis | journal = Current Opinion in Rheumatology | volume = 28 | issue = 6 | pages = 625–630 | date = November 2016 | pmid = 27454210 | doi = 10.1097/BOR.0000000000000326 | s2cid = 25027014 }}</ref> allowing painless, non-invasive visualisation of any muscle wastage.<ref name="Hoffman_2021" />
Muscle biopsies, however, are the most reliable tests for diagnosing myositis.<ref name="Hoffman_2021" />
There are also a variety of blood tests available that help in the diagnosis of myositis. The doctor may look for an elevation of creatine kinase in the blood, which is indicative of muscle inflammation.<ref name="Hoffman_2021" /> Certain autoantibodies (antibodies that target muscle cells) can also be found in the blood, which can indicate that myositis is caused by an autoimmune disease.<ref name="Betteridge_2016" /> Some specific examples of autoantibodies are Anti-Jo-1, Anti-HMGCR, Anti-TIF1, etc.<ref name="Betteridge_2016" />
==Treatment== Treatment for myositis depends on the underlying cause.<ref name="Hoffman_2021" /> For myositis, which is caused by a viral infection, no treatment is typically needed.<ref name="Hoffman_2021" /> For myositis caused by a bacterial infection, antibiotics can be used.<ref name="Hoffman_2021" /> For myositis caused by a medication, it is important to stop using that medication.<ref name="Hoffman_2021" />
There are a variety of treatment options available if myositis is caused by an autoimmune disease. Glucocorticoids are often the first choice for treatment.<ref name="Sasaki_2018">{{cite journal | vauthors = Sasaki H, Kohsaka H | title = Current diagnosis and treatment of polymyositis and dermatomyositis | journal = Modern Rheumatology | volume = 28 | issue = 6 | pages = 913–921 | date = November 2018 | pmid = 29669460 | doi = 10.1080/14397595.2018.1467257 | s2cid = 4934267 }}</ref> This drug works to weaken the immune system so that it is not able to attack the muscles. It is a type of steroid and can cause a wide array of side effects, such as mood changes, increased hunger, trouble sleeping, etc. Another treatment option is a steroid-sparing immunosuppressive agent.<ref name="Sasaki_2018" /> This also works to weaken the immune system but does not cause the side effects that steroids do. Another treatment option is a class of drugs called biologics.<ref name="Sasaki_2018" /> Also, intravenous immunoglobulins (IVIg) have been shown to be effective in the treatment of myositis caused by an autoimmune disease.<ref>{{cite journal | vauthors = Mulhearn B, Bruce IN | title = Indications for IVIG in rheumatic diseases | journal = Rheumatology | volume = 54 | issue = 3 | pages = 383–391 | date = March 2015 | pmid = 25406359 | pmc = 4334686 | doi = 10.1093/rheumatology/keu429 }}</ref>
== See also == * Benign acute childhood myositis * Inflammatory myopathies * Myopathy (muscle disease) * Myalgia (muscle pain) * Masticatory muscle myositis (a disease in dogs) * Perimyositis * Sarcoidosis § Bones, joints, and muscles
== References == {{reflist}}
== External links == * [https://www.medlineplus.gov/myositis.html Myositis]: NIH {{Medical resources | DiseasesDB = 29473 | ICD10 = {{ICD10|M|60||m|60}} | ICD9 = {{ICD9|729.1}} | ICDO = | OMIM = 160750 | MedlinePlus = 001245 | eMedicineSubj = | eMedicineTopic = | MeshID = D009220 }}
{{Systemic connective tissue disorders}} {{Myopathy}}
Myositis Association https://www.myositis.org
Category:Inflammations Category:Muscular disorders