Polymyositis (PM) is a type of chronic

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

of the muscles (

inflammatory myopathy Inflammatory myopathy is disease featuring weakness and inflammation of muscles and (in some types) muscle pain. The cause of much inflammatory myopathy is unknown (idiopathic), and such cases are classified according to their symptoms and signs ...

) related to dermatomyositis and inclusion body myositis. Its name means "inflammation of many muscles" ('' poly-'' + '' myos-'' + '' -itis''). The inflammation of polymyositis is mainly found in the endomysial layer of skeletal muscle, whereas dermatomyositis is characterized primarily by inflammation of the perimysial layer of skeletal muscles.

Signs and symptoms

The hallmark of polymyositis is weakness and/or loss of muscle mass in the proximal musculature, as well as flexion of the neck and torso. These symptoms can be associated with marked pain in these areas as well. The hip extensors are often severely affected, leading to particular difficulty in climbing stairs and rising from a seated position. The skin involvement of dermatomyositis is absent in polymyositis.

Dysphagia Dysphagia is difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right. It may be a sensation that suggests difficulty in the passage of solids or liq ...

(difficulty swallowing) or other problems with esophageal

motility Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

occur in as many as 1/3 of patients. Low grade fever and enlarged lymph nodes may be present. Foot drop in one or both feet can be a symptom of advanced polymyositis and inclusion body myositis. The systemic involvement of polymyositis includes

interstitial lung disease Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue and space around the alveoli (air sacs)) of the lungs. It concerns alveolar epithelium, pu ...

(ILD) and heart disease, such as heart failure and conduction abnormalities. 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 as an inability to rise from a seated position without help or an inability to raise one's arms above one's head. The weakness is generally progressive, accompanied by lymphocytic inflammation (mainly cytotoxic T cells).

Associated illnesses

Polymyositis and the associated inflammatory myopathies have an associated increased risk of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

. The features they found associated with an increased risk of cancer were older age, age greater than 45, male sex,

difficulty swallowing Dysphagia is difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right. It may be a sensation that suggests difficulty in the passage of solids or liqui ...

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

of skin cells, cutaneous vasculitis, rapid onset of myositis (<4 weeks), elevated

creatine kinase Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create pho ...

, higher erythrocyte sedimentation rate and higher

C-reactive protein C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin- ...

levels. Several factors were associated with lower-than-average risk, including the presence of interstitial lung disease, joint inflammation/

joint pain Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...

Raynaud's syndrome Raynaud syndrome, also known as Raynaud's phenomenon, eponymously named after the physician Auguste Gabriel Maurice Raynaud, who first described it in his doctoral thesis in 1862, is a medical condition in which the spasm of small arteries cau ...

, or anti-Jo-1 antibody. The malignancies that are associated are nasopharyngeal cancer,

lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, malign ...

non-Hodgkin's lymphoma Non-Hodgkin lymphoma (NHL), also known as non-Hodgkin's lymphoma, is a group of hematological malignancy, blood cancers that includes all types of lymphomas except Hodgkin lymphomas. Symptoms include lymphadenopathy, enlarged lymph nodes, fever ...

and

bladder cancer Bladder cancer is any of several types of cancer arising from the tissues of the urinary bladder. Symptoms include blood in the urine, pain with urination, and low back pain. It is caused when epithelial cells that line the bladder become ma ...

, amongst others. Cardiac involvement manifests itself typically as heart failure and is present in up to 77% of patients. Interstitial lung disease is found in up to 65% of patients with polymyositis, as defined by HRCT or restrictive ventilatory defects compatible with interstitial lung disease.

Causes

Polymyositis is an inflammatory myopathy mediated by cytotoxic T cells with an as yet unknown

autoantigen In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease". ...

, while dermatomyositis is a humorally mediated

angiopathy Angiopathy is the generic term for a disease of the blood vessels (arteries, veins, and capillaries). The best known and most prevalent angiopathy is diabetic angiopathy, a common complication of chronic diabetes. Classification By caliber Ther ...

resulting in myositis and a typical dermatitis. The cause of polymyositis is unknown and may involve viruses and autoimmune factors. Cancer may trigger polymyositis and dermatomyositis, possibly through an immune reaction against cancer that also attacks a component of muscles. There is tentative evidence of an association with

celiac disease Coeliac disease (British English) or celiac disease (American English) is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barle ...

Diagnosis

Diagnosis is fourfold: History and physical examination, elevation of

, electromyograph (EMG) alteration, and a positive muscle biopsy. The hallmark clinical feature of polymyositis is proximal muscle weakness, with less important findings being muscle pain and dysphagia. Cardiac and pulmonary findings will be present in approximately 25% of cases of patients with polymyositis. Sporadic inclusion body myositis (sIBM) is often misdiagnosed as polymyositis or dermatomyositis but it can be differentiated as myositis that does not respond to treatment is likely IBM. sIBM comes on over months to years; polymyositis comes on over weeks to months. Polymyositis tends to respond well to treatment, at least initially; IBM does not.

Treatment

The first line treatment for polymyositis is corticosteroids. Specialized exercise therapy may supplement treatment to enhance quality of life.

Epidemiology

Polymyositis strikes females with greater frequency than males.

Polymyositis as a distinct diagnosis

The discovery of several myositis-specific autoantibodies during the past decades has enabled the description of other discrete subsets of diagnosis, specifically the discovery of Antisynthetase syndrome in reducing the number of diagnoses of polymyositis.

Society and culture

Notable cases

* Dan Christensen, painter of abstract art. Died due to heart failure caused by polymyositis. *

Robert Erickson Robert Erickson (March 7, 1917 – April 24, 1997) was an American composer. Education Erickson was born in Marquette, Michigan. He studied with Ernst Krenek from 1936 to 1947: "I had already studied—and abandoned—the twelve tone sys ...

, American composer and teacher who was a leading modernist exponent of "12-tone" composition. Died from the effects of polymyositis. * David Lean, film director. * Eric Samuelsen, playwright. * Victor Manuel Resendiz Ruiz, wrestler. * Cardinal John Wright

References

External links

{{Systemic connective tissue disorders Inflammations Steroid-responsive inflammatory conditions Systemic connective tissue disorders