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| {{Infobox_Disease
| | #REDIRECT[[Polymyositis and dermatomyositis]] |
| | Name = {{PAGENAME}}
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| | Image = XRaydermatomyositis.jpg
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| | Caption = X-Ray of the knee in a patient with dermatomyositis.
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| | DiseasesDB = 10343
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| | ICD10 = {{ICD10|M|33|0|m|30}}-{{ICD10|M|33|1|m|30}}
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| | ICD9 = {{ICD9|710.3}}
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| | ICDO =
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| | OMIM =
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| | MedlinePlus = 000839
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| | eMedicineSubj = med
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| | eMedicineTopic = 2608
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| | eMedicine_mult = {{eMedicine2|derm|98}}
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| | MeshID = D003882
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| }}
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| {{SI}}
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| {{CMG}}
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| '''Associate Editor-In-Chief:''' {{CZ}}
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| {{Editor Join}}
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| ===[[The Heart in Polymyositis and Dermatomyositis|for the heart in Dermatomyositis click here]]===
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| ==Overview==
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| '''Dermatomyositis''' is connective-tissue disease that is characterized by [[inflammation]] of the muscles and the skin. Its cause is unknown, but it may result from either a viral infection or an [[autoimmune]] reaction. Up to 50% of the cases may be a [[paraneoplastic phenomenon]], indicating the presence of [[cancer]].
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| [[X-ray]] findings include dystrophic [[calcification]]s in the muscles.
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| There is a form of this disorder that strikes children, known as [[juvenile dermatomyositis]].
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| "Gottron's papules", pink patches on the knuckles, and priapism, are associated with this disorder.
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| ==Pathology==
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| The diagnosis of dermatomyositis can be confirmed by muscle biopsy. There are two classic microscopic findings of dermatomyositis. They are:
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| * A mixed [[B-cell |B-]] and [[T-cell]] perivascular inflammatory infiltrate
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| * Perifascicular muscle fiber atrophy
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| ==Causes==
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| The cause is unknown, but it may result from either a viral infection or an [[autoimmune]] reaction. Some cases of dermatomyositis actually "overlap" (are combined with) another autoimmune disease such as [[lupus]], [[scleroderma]], or [[vasculitis]]. Because of the link between DM and autoimmune disease, doctors and patients suspecting DM may find it helpful to run an ANA - antinuclear antibody - test, which in cases of a [[lupus]]-like nature may be positive (usually from 1:160 to 1:640, with normal ranges at 1:40 and below).{{Fact|date=February 2009}}
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| Some cases of DM are a [[paraneoplastic phenomenon]], indicating the presence of [[cancer]].<ref name="pmid16603844">{{cite journal | author=Scheinfeld NS | title=Ulcerative paraneoplastic dermatomyositis secondary to metastatic breast cancer | journal=Skinmed | volume=5 | issue=2 | pages=94–6 | year=2006 | pmid=16603844 | url=http://www.lejacq.com/articleDetail.cfm?pid=SKINmed_5;2:94 | doi=10.1111/j.1540-9740.2006.03637.x}}</ref> In cases involving cancer, the cancer is usually pre-existent, with removal of the cancer resulting in remission of the DM. The onset of a rash in patients with pre-existing myositis requires investigation of the neoplastic possibility.
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| In 1988, the noted Lyme disease researcher Dr. Alan Steere observed: "Finally, the perivascular lymphoid infiltrate in clinical myositis does not differ from that seen in polymyositis or dermatomyositis. All of these histologic derangements suggest immunologic damage in response to persistence of the spirochete, however few in number.", in his article, ''Clinical pathologic correlations of Lyme disease by stage.''
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| ==Microscopic findings==
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| Cross sections of muscle reveal muscle fascicles with small, shrunken polygonal muscle fibers on the periphery of a fascicle surrounding central muscle fibers of normal, uniform size.
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| Aggregates of mature [[lymphocytes]] with small, dark nuclei and scant cytoplasm are seen surrounding vessels. Other inflammatory cells are distinctly uncommon. [[Immunohistochemistry]] can be used to demonstrate that both B- and T-cells are present in approximately equal numbers.<ref>Benveniste O, Squier W, Boyer O, Hilton-Jones D, Herson S. ''Presse Med''. '''2004''' Nov 20;33(20):1444-50. PMID: 15611679</ref> <ref>Nirmalananthan N, Holton JL, Hanna MG. Is it really myositis? A consideration of the differential diagnosis. ''Curr Opin Rheumatol''. '''2004''' Nov;16(6):684-91.</ref>
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| ==Mechanism==
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| The mechanism is conjectured to be [[Complement system |complement]]-mediated damage of microscopic vessels with muscle atrophy and lymphocytic inflammation secondary to tissue [[ischemia]] {{Ref|Benveniste2004}}.
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| == Diagnosis ==
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| === History and Symptoms ===
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| Periorbital Heliotrope Rash (HELIOTROPE RASH: purple /erythematous rash affecting eyelids, malar, forehead and nasolabial folds), Gottron's papules at the knuckles (Purple /erythematous raised lesions over knuckles and extensor regions).
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| === Physical Examination ===
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| [[Image:heliotrope_rash_(Dermatomyositis).jpg|thumb|200px|left|Heliotrope rash (Dermatomyositis) Prox muscle weakness
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| <ref>http://picasaweb.google.com/mcmumbi/USMLEIIImages/photo#5089143195781344626</ref>]]
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| <br clear="left"/>
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| ==Differential Diagnosis ==
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| Dermatomyositis must be differentiated from other common, lymphocyte predominant inflammatory myopathies. If present, the characteristic perifascicular atrophy makes this distinction trivial.
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| There is some overlap in the microscopic appearances of different inflammatory myopathies, but some helpful differences are often present.{{Ref|Nirmalananthan2004}} The rimmed vacuoles of [[Inclusion body myositis|inclusion body myositis]] (IBM) are absent in dermatomyositis. Polymyositis is characterised by diffuse or patchy inflammation of the muscle fascicles, a random pattern of muscle atrophy, and T-cell predominance with T-cells seen invading otherwise viable appearing muscle fibers.{{Ref|Benveniste2004}}
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| ==Treatment==
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| * 1. High Dose [[Prednisolone]]
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| * 2. [[Methotrexate]] (complication: may cause [[Interstitial lung disease]])
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| * 3. [[IVIG]]
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| * 4. [[Azathioprine]]
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| * 5. [[Cyclophosphamide]]
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| ==References==
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| {{reflist}}
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| == External links ==
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| * [http://www.rheumatology.org/public/factsheets/myopathies_new2.asp?aud=pat The American College of Rheumatology's patient education page on myopathy]
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| * [http://tray.dermatology.uiowa.edu/DIB/DM-004.htm Illustration of Gottron's papules]
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| {{Muscular Dystrophy}}
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| {{Diseases of the musculoskeletal system and connective tissue}}
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| {{SIB}}
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| <br>
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| [[de:Dermatomyositis]]
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| [[es:Dermatomiositis]]
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| [[nl:Dermatomyositis]]
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| [[ja:皮膚筋炎]]
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| [[pl:Dermatomyositis]]
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| [[Category:Dermatology]]
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| [[Category:Diseases involving the fasciae]]
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| [[Category:Inflammations]]
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| [[Category:Autoimmune diseases]]
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| [[Category:Rheumatology]]
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| [[Category:Signs and symptoms]]
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