Dermatomyositis
| Dermatomyositis | |
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| X-Ray of the knee in a patient with dermatomyositis. | |
| ICD-10 | M33.0-M33.1 |
| ICD-9 | 710.3 |
| DiseasesDB | 10343 |
| MedlinePlus | 000839 |
| eMedicine | med/2608 derm/98 |
| MeSH | D003882 |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]
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Overview
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.
X-ray findings include dystrophic calcifications in the muscles.
There is a form of this disorder that strikes children, known as juvenile dermatomyositis.
"Gottron's papules", pink patches on the knuckles, and priapism, are associated with this disorder.
Pathology
The diagnosis of dermatomyositis can be confirmed by muscle biopsy. There are two classic microscopic findings of dermatomyositis. They are:
Causes
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).[citation needed]
Some cases of DM are a paraneoplastic phenomenon, indicating the presence of cancer.[1] 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.
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.
Microscopic findings
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.
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.[2] [3]
Mechanism
The mechanism is conjectured to be complement-mediated damage of microscopic vessels with muscle atrophy and lymphocytic inflammation secondary to tissue ischemia [4].
Diagnosis
History and Symptoms
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).
Physical Examination
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Differential Diagnosis
Dermatomyositis must be differentiated from other common, lymphocyte predominant inflammatory myopathies. If present, the characteristic perifascicular atrophy makes this distinction trivial.
There is some overlap in the microscopic appearances of different inflammatory myopathies, but some helpful differences are often present.[5] The rimmed vacuoles of 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.[6]
Treatment
- 1. High Dose Prednisolone
- 2. Methotrexate (complication: may cause Interstitial lung disease)
- 3. IVIG
- 4. Azathioprine
- 5. Cyclophosphamide
References
- ↑ Scheinfeld NS (2006). "Ulcerative paraneoplastic dermatomyositis secondary to metastatic breast cancer". Skinmed. 5 (2): 94–6. doi:10.1111/j.1540-9740.2006.03637.x. PMID 16603844.
- ↑ Benveniste O, Squier W, Boyer O, Hilton-Jones D, Herson S. Presse Med. 2004 Nov 20;33(20):1444-50. PMID: 15611679
- ↑ 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.
- ↑ http://picasaweb.google.com/mcmumbi/USMLEIIImages/photo#5089143195781344626
External links
- The American College of Rheumatology's patient education page on myopathy
- Illustration of Gottron's papules
Template:Muscular Dystrophy
Template:Diseases of the musculoskeletal system and connective tissue
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