Inflammatory myopathy

Last updated
Inflammatory myopathy
Other namesIdiopathic inflammatory myopathy
Dermatomyositis.jpg
Gottron's papules on the hand of a patient with juvenile dermatomyositis
Specialty Rheumatology   OOjs UI icon edit-ltr-progressive.svg

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 (idiopathic), and such cases are classified according to their symptoms and signs, electromyography, MRI, and laboratory findings. It can also be associated with underlying cancer. The main classes of idiopathic inflammatory myopathy are polymyositis (PM), dermatomyositis (DM) (including juvenile, amyopathic, and sine-dermatitis form), inclusion-body myositis (IBM), immune-mediated necrotising myopathy (IMNM), and focal autoimmune myositis. [1]

Contents

Diagnosis

Idiopathic inflammatory myopathy is a diagnosis of exclusion. There are a number of known causes of myopathy, and it is only once these have been ruled out that a clinician should assign an idiopathic inflammatory myopathy. The usual criteria for a diagnosis of PM are weakness in muscles of the head, neck, trunk, upper arms or upper legs; raised blood serum concentrations of some muscle enzymes such as creatine kinase; unhealthy muscle changes on electromyography; and biopsy findings of (i) muscle cell degeneration and regeneration and (ii) chronic inflammatory infiltrates in muscle cells. If heliotrope (purple) rash or Gottron's papules are also present, then the diagnosis is DM. In DM, myositis may not be clinically apparent but detectable via biopsy or MRI. [2] If the criteria for PM are met but muscle weakness also affects the hands and feet or is not accompanied by pain IBM should be suspected, and confirmed when muscle cell biopsy reveals (i) cytoplasmic vacuoles fringed by basophilic granules and (ii) inflammatory infiltrate comprising mostly CD8 T lymphocytes and macrophages; and electron microscopy reveals filamentous 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 corticosteroid (methylprednisolone) may be used; but normally treatment begins with a single daily (after breakfast) high dose of oral corticosteroid (prednisone). After a month or so the strength of every second day's dose is very gradually reduced over three to four months, to minimize the negative effects of the prednisone. When a high dose of prednisone cannot be reduced without losing muscle strength, or when prednisone is effective but it is producing significant complications, "steroid sparing" oral immunosuppressants such as azathioprine, mycophenolate mofetil, methotrexate and 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 immunoglobulin, ciclosporin, tacrolimus, 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:

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

Related Research Articles

Inclusion body myositis (IBM) is the most common inflammatory muscle disease in older adults. The disease is characterized by slowly progressive weakness and wasting of both proximal muscles and distal muscles, most apparent in the finger flexors and knee extensors. IBM is often confused with an entirely different class of diseases, called hereditary inclusion body myopathies (hIBM). The "M" in hIBM is an abbreviation for "myopathy" while the "M" in IBM is for "myositis". In IBM, two processes appear to occur in the muscles in parallel, one autoimmune and the other degenerative. Inflammation is evident from the invasion of muscle fibers by immune cells. Degeneration is characterized by the appearance of holes, deposits of abnormal proteins, and filamentous inclusions in the muscle fibers. sIBM is a rare disease, with a prevalence ranging from 1 to 71 individuals per million.

<span class="mw-page-title-main">Myasthenia gravis</span> Autoimmune disease resulting in skeletal muscle weakness

Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, drooping eyelids, and difficulties in talking and walking. Onset can be sudden. Those affected often have a large thymus or develop a thymoma.

<span class="mw-page-title-main">Optic neuritis</span> Medical condition

Optic neuritis describes any condition that causes inflammation of the optic nerve; it may be associated with demyelinating diseases, or infectious or inflammatory processes.

<span class="mw-page-title-main">Myalgia</span> Painful sensations in muscle tissue

Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, especially when there has been no injury.

<span class="mw-page-title-main">Juvenile dermatomyositis</span> Medical condition

Juvenile dermatomyositis (JDM) is an idiopathic inflammatory myopathy (IMM) of presumed autoimmune dysfunction resulting in muscle weakness among other complications. It manifests itself in children; it is the pediatric counterpart of dermatomyositis. In JDM, the body's immune system attacks blood vessels throughout the body, causing inflammation called vasculitis. In the United States, the incidence rate of JDMS is approximately 2-3 cases per million children per year. The UK incidence is believed to be between 2-3 per million children per year, with some difference between ethnic groups. The sex ratio is approximately 2:1. Other Idiopathic inflammatory myopathies include; juvenile polymyositis (PM), which is rare and not as common in children as in adults.

<span class="mw-page-title-main">Dermatomyositis</span> Long-term inflammatory disorder of the skin and muscles

Dermatomyositis (DM) is a long-term inflammatory disorder which affects the skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may include weight loss, fever, lung inflammation, or light sensitivity. Complications may include calcium deposits in muscles or skin.

In medicine, myopathy is a disease of the muscle in which the muscle fibers do not function properly. Myopathy means muscle disease. This meaning implies that the primary defect is within the muscle, as opposed to the nerves or elsewhere.

<span class="mw-page-title-main">Polymyositis</span> Medical condition

Polymyositis (PM) is a type of chronic inflammation of the muscles related to dermatomyositis and inclusion body myositis. Its name means 'inflammation of many muscles'. 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.

<span class="mw-page-title-main">Myositis</span> Medical condition

Myositis is a rarely-encountered medical condition characterized by inflammation affecting the muscles. The manifestations of this condition may include skin issues, muscle weakness, and the potential involvement of other organs. Additionally, systemic symptoms like weight loss, fatigue, and low-grade fever can manifest in individuals with myositis.

<span class="mw-page-title-main">Masticatory muscle myositis</span>

Masticatory muscle myositis (MMM) is an inflammatory disease in dogs affecting the muscles of mastication (chewing). It is also known as atrophic myositis or eosinophilic myositis. MMM is the most common inflammatory myopathy in dogs. The disease mainly affects large breed dogs. German Shepherd Dogs and Cavalier King Charles Spaniels may be predisposed. There is a similar disease of the eye muscles found in Golden Retrievers. Symptoms of acute MMM include swelling of the jaw muscles, drooling, and pain on opening the mouth. Ophthalmic signs may include third eyelid protrusion, red eyes, and exophthalmos. In chronic MMM there is atrophy of the jaw muscles, and scarring of the masticatory muscles due to fibrosis may result in inability to open the mouth (trismus). The affected muscles include the temporalis, masseter, and pterygoid muscles. The disease is usually bilateral.

<span class="mw-page-title-main">Chronic inflammatory demyelinating polyneuropathy</span> Medical condition

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes called chronic relapsing polyneuropathy (CRP) or chronic inflammatory demyelinating polyradiculoneuropathy. CIDP is closely related to Guillain–Barré syndrome and it is considered the chronic counterpart of that acute disease. Its symptoms are also similar to progressive inflammatory neuropathy. It is one of several types of neuropathy.

Mixed connective tissue disease (MCTD) is a systemic autoimmune disease that shares characteristics with at least two other systemic autoimmune diseases, including systemic sclerosis (Ssc), systemic lupus erythematosus (SLE), polymyositis/dermatomyositis (PM/DM), and rheumatoid arthritis. The idea behind the "mixed" disease is that this specific autoantibody is also present in other autoimmune diseases such as systemic lupus erythematosus, polymyositis, scleroderma, etc. MCTD was characterized as an individual disease in 1972 by Sharp et al., and the term was introduced by Leroy in 1980.

<span class="mw-page-title-main">Deflazacort</span> Pharmaceutical drug

Deflazacort is a glucocorticoid belonging to acetonides or O-isopropylidene derivative. It is used as an anti-inflammatory and was patented in 1969 and approved for medical use in 1985. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication for Duchenne Muscular Dystrophy.

Scleromyositis, is an autoimmune disease. People with scleromyositis have symptoms of both systemic scleroderma and either polymyositis or dermatomyositis, and is therefore considered an overlap syndrome. Although it is a rare disease, it is one of the more common overlap syndromes seen in scleroderma patients, together with MCTD and Antisynthetase syndrome. Autoantibodies often found in these patients are the anti-PM/Scl (anti-exosome) antibodies.

<span class="mw-page-title-main">HLA-DR17</span>

HLA-DR17 (DR17) is an HLA-DR serotype that recognizes the DRB1*0301 and *0304 gene products. DR17 is found at high frequency in Western Europe. DR17 is part of the broader antigen group HLA-DR3 and is very similar to the group HLA-DR18.

<span class="mw-page-title-main">Kimura's disease</span> Medical condition

Kimura's disease is a benign rare chronic inflammatory disorder. Its primary symptoms are subdermal lesions in the head or neck or painless unilateral inflammation of cervical lymph nodes.

Although they vary in particulars, polymyositis, dermatomyositis and inclusion body myositis are idiopathic inflammatory myopathies (IIM) primarily characterized by chronic inflammation of human skeletal muscle tissue that ultimately causes the necrosis of muscle cells. This degeneration leads to muscle tissue wasting, weakness and fatigue among other serious effects. Until recently, exercise has been avoided as a type of therapy, and even forbidden due to the risk of triggering or amplifying inflammation. However, several studies have been conducted to test this assumption and have shown that aerobic exercise as well as resistance training can maintain and even improve quality of life for IIM-affected individuals without increased inflammatory response.

<span class="mw-page-title-main">Acquired non-inflammatory myopathy</span> Medical condition

Acquired non-inflammatory myopathy (ANIM) is a neuromuscular disorder primarily affecting skeletal muscle, most commonly in the limbs of humans, resulting in a weakness or dysfunction in the muscle. A myopathy refers to a problem or abnormality with the myofibrils, which compose muscle tissue. In general, non-inflammatory myopathies are a grouping of muscular diseases not induced by an autoimmune-mediated inflammatory pathway. These muscular diseases usually arise from a pathology within the muscle tissue itself rather than the nerves innervating that tissue. ANIM has a wide spectrum of causes which include drugs and toxins, nutritional imbalances, acquired metabolic dysfunctions such as an acquired defect in protein structure, and infections.

<span class="mw-page-title-main">Antisynthetase syndrome</span> Medical condition

Antisynthetase syndrome (ASS) is a multisystematic autoimmune disease associated with inflammatory myositis, interstitial lung disease, and antibodies directed against various synthetases of aminoacyl-transfer RNA. Other common symptoms include mechanic's hands, Raynaud's phenomenon, arthritis, and fever.

Statin-associated autoimmune myopathy (SAAM), also known as anti-HMGCR myopathy, is a very rare form of muscle damage caused by the immune system in people who take statin medications. However, there are cases of SAAM in patients who have not taken statin medication, and this can be explained by the exposure to natural sources of statin such as red yeast rice, which is statin rich. This theory is supported by the higher prevalence of statin-naive SAAM patients in Asian cohorts, who have statin-rich diets.

References

  1. 1 2 3 4 5 Szczęsny P, Świerkocka K, Olesińska M (2018). "Differential diagnosis of idiopathic inflammatory myopathies in adults - the first step when approaching a patient with muscle weakness". Reumatologia. 56 (5): 307–315. doi:10.5114/reum.2018.79502. PMC   6263305 . PMID   30505013.
  2. Miller FW (10 June 2009). "Classification of Idiopathic Inflammatory Myopathies". In Kagen LJ (ed.). The Inflammatory Myopathies. Springer. pp. 23–36. ISBN   9781627038393.
  3. Kagen LJ (10 June 2009). "Inclusion Body Myositis". In Kagen LJ (ed.). The Inflammatory Myopathies. Springer. pp. 95–102. ISBN   9781627038393.
  4. 1 2 3 4 Holton JL, Wedderburn LR, Hanna MG (29 May 2013). "Polymyositis, Dermatomyositis and Inclusion Body Myositis". In Goebel HH, Sewry CA, Weller RO (eds.). Muscle Disease: Pathology and Genetics. John Wiley & Sons. pp. 747–781. ISBN   978-1-118-63549-0.
  5. 1 2 3 4 5 Dalakas MC (8 September 2010). "Treatment and Management of Autoimmune Myopathies". In Bertorini TE (ed.). Neuromuscular Disorders. Elsevier Health Sciences. pp. 395–408. ISBN   9781437703726.
  6. Cited in Dalakas, Marinos C (08 September 2010). "Treatment and Management of Autoimmune Myopathies". In Bertorini, Tulio E. Neuromuscular Disorders. Elsevier Health Sciences. pp. 395—408. ISBN   9781437703726:
    • Dalakas MC, Sonies B, Dambrosia J, Sekul E, Cupler E, Sivakumar K (March 1997). "Treatment of inclusion-body myositis with IVIg: a double-blind, placebo-controlled study". Neurology. 48 (3): 712–716. doi:10.1212/wnl.48.3.712. PMID   9065553. S2CID   25118314.
    • Walter MC, Lochmüller H, Toepfer M, Schlotter B, Reilich P, Schröder M, et al. (January 2000). "High-dose immunoglobulin therapy in sporadic inclusion body myositis: a double-blind, placebo-controlled study". Journal of Neurology. 247 (1): 22–28. doi:10.1007/s004150050005. PMID   10701893. S2CID   23409201.
    • Cherin P, Pelletier S, Teixeira A, Laforet P, Simon A, Herson S, Eymard B (January 2002). "Intravenous immunoglobulin for dysphagia of inclusion body myositis". Neurology. 58 (2): 326. doi:10.1212/wnl.58.2.326. PMID   11805271. S2CID   40526855.
  7. Spector SA, Lemmer JT, Koffman BM, Fleisher TA, Feuerstein IM, Hurley BF, Dalakas MC (October 1997). "Safety and efficacy of strength training in patients with sporadic inclusion body myositis". Muscle & Nerve. 20 (10): 1242–1248. doi:10.1002/(sici)1097-4598(199710)20:10<1242::aid-mus6>3.3.co;2-x. PMID   9324080. Cited in:
    • Dalakas, Marinos C (08 September 2010). "Treatment and Management of Autoimmune Myopathies". In Bertorini, Tulio E. Neuromuscular Disorders. Elsevier Health Sciences. pp. 395—408. ISBN   9781437703726
  8. Mastaglia FL, Garlepp MJ, Phillips BA, Zilko PJ (April 2003). "Inflammatory myopathies: clinical, diagnostic and therapeutic aspects". Muscle & Nerve. 27 (4): 407–425. doi:10.1002/mus.10313. PMID   12661042. S2CID   24978554. Cited in:
    • Holton JL, Wedderburn LR, Hanna MG (29 May 2013). "Polymyositis, Dermatomyositis and Inclusion Body Myositis". In Goebel HH, Sewry CA, Weller RO (eds.). Muscle Disease: Pathology and Genetics. John Wiley & Sons. pp. 747–781. ISBN   978-1-118-63549-0.
  9. Tarnopolsky MA, Hatcher E, Shupak R (May 2016). "Genetic Myopathies Initially Diagnosed and Treated as Inflammatory Myopathy". The Canadian Journal of Neurological Sciences. Le Journal Canadien des Sciences Neurologiques. 43 (3): 381–384. doi: 10.1017/cjn.2015.386 . PMID   26911292. S2CID   25515951.
  10. 1 2 Bhai SF, Dimachkie MM, de Visser M (June 2022). "Is it really myositis? Mimics and pitfalls". Best Practice & Research. Clinical Rheumatology. 36 (2): 101764. doi:10.1016/j.berh.2022.101764. PMID   35752578. S2CID   250012951.
  11. Baer AN, Wortmann RL (May 2013). "Noninflammatory myopathies". Rheumatic Disease Clinics of North America. 39 (2): 457–479. doi:10.1016/j.rdc.2013.02.006. PMID   23597974.