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Dermatomyositis (DM) is a connective-tissue disease related to polymyositis (PM) that is characterized by inflammation of the muscles and the skin. While DM most frequently affects the skin and muscles, it is a systemic disorder that may also affect the joints, the esophagus, the lungs, and the heart. In the United States, the incidence of DM is estimated at 5.5 cases per million people.〔http://www.bio.davidson.edu/courses/immunology/students/spring2003/statler/dermatomyositis.htm.〕 == Signs and symptoms == The main symptoms include skin rash and symmetric proximal muscle weakness (in over 90% of patients〔Bohan A, Peter JB, Bowman RL, Pearson CM. Computer-assisted analysis of 153 patients with polymyositis and dermatomyositis. Medicine (Baltimore). 1977;56(4):255.〕) which may be accompanied by pain. The pain may resemble the type experienced after strenuous exercise. Some dermatomyositis patients have little pain, while in others (esp. in juvenile dermatomyositis), the pain may be severe. It is important to remember that this condition varies from person to person in many ways. Also in many cases muscle may deteriorate and render the patient temporarily paralyzed unable to walk, run, get out of bed, or even swallow food and liquids. Skin findings occur in dermatomyositis but not PM and are generally present at diagnosis. ''Gottron's sign'' is an erythematous, scaly eruption occurring in symmetric fashion over the MCP and interphalangeal joints (can mimic psoriasis). The heliotrope or "lilac" rash〔Page 151 in: 8th edition.〕 is a violaceous eruption on the upper eyelids and in rare cases on the lower eyelids as well, often with itching and swelling (most specific, though uncommon). Shawl (or V-) sign is a diffuse, flat, erythematous lesion over the back and shoulders or in a "V" over the posterior neck and back or neck and upper chest, which worsens with UV light. Erythroderma is a flat, erythematous lesion similar to the shawl sign but located in other areas, such as the malar region and the forehead. Periungual telangiectasias and erythema occur. "Mechanic's hands" (also in PM) refers to rough, cracked skin at the tips and lateral aspects of the fingers forming irregular dirty-appearing lines that resemble those seen in a laborer (this is also associated with the anti-synthetase syndrome). See: sclerodactyly. Psoriaform changes in the scalp can occur. Centripetal flagellate erythema comprises linear, violaceous streaks on the trunk (possibly caused by itching pruritic skin). Calcinosis cutis (deposition of calcium in the skin) is usually seen in juvenile dermatomyositis, not adult dermatomyositis. Dysphagia (difficulty swallowing) is another feature, occurring in as many as 33% of cases. Dermatomyositis occurs more commonly in female patients. The initial symptoms may vary considerably, from dysphagia (difficulty swallowing), feverish sensations, and most often proximal symmetrical muscle weakness with vasculitis affecting the skin, muscles and internal organs. Patients find it hard to raise their arms to comb their hair or walk up the stairs due to the proximal muscle weakness. It can be severe enough to affect the muscles needed for speech and/or swallowing and is also known to cause respiratory compromise (due to a variety of mechanisms). Calcinosis can occur in the skin, joints and tissues. ESR and CPK tend to be elevated, along with typical EMG findings of spontaneous muscle fibrillation and short polyphasic muscle potentials. However, the findings may be variable if the disease affects only patches of muscle and/or overlaps with an autoimmune disease. Definitive diagnosis is through muscle biopsy, which may isolate the type of disease and severity of involvement. When present, Gottron's papules — scaly erythematous eruptions or red patches overlying the knuckles, elbows, and knees — are characteristic of dermatomyositis, though not seen in every patient. Other skin manifestations involve periungual telangiectasias and a heliotrope (purple) rash over the upper eyelids. The rash over the upper eyelids may be the only sign of skin involvement in some cases. File:Dermatomyositis2.jpg|Gottron's papules. Erythematous to violaceous raised papules overlying the metacarpal and interphalangeal joints in a patient with juvenile dermatomyositis. File:Dermatomyositis3.jpg|Gottron's papules. Characteristic raised erythematous papule overlying the proximal interphalangeal joint in a patient with dermatomyositis. File:Dermatomyositis4.jpg|Gottron's papules. Erythematous plaques overlying the elbows in a patient with juvenile dermatomyositis. In some patients, small erythematous plaques may overly the extensor aspects of larger joints, such as the elbows, knees, and medial malleoli. This is considered to be an extended part of the spectrum of Gottron's papules. File:Dermatomyositis5.jpg|Gottron's papules. Erythematous plaques overlying the elbows in a patient with juvenile dermatomyositis. In some patients, small erythematous plaques may overly the extensor aspects of larger joints, such as the elbows, knees, and medial malleoli. This is considered to be an extended part of the spectrum of Gottron's papules. Note in Figure, a focal area of dystrophic calcification at the site of Gottron's papules, which is indicative of damage, as discussed below. File:Dermatomyositis6.jpg|Gottron's papules with telangiectasia. Gottron's papules with prominent atrophy, porcelain white scarring, and telangiectasia. File:Dermatomyositis8.jpg|Gottron's sign. Confluent macular erythema with scale confined to the skin overlying the patellae in a girl with juvenile dermatomyositis. File:Dermatomyositis7.jpg|Gottron's papules showing secondary atrophy and telangiectasia in a girl with severe juvenile dermatomyositis. These changes are seen in association with prominent periungual erythema, a cutaneous finding indicative of ongoing disease activity. File:Dermatomyositis9.jpg|Heliotrope. Confluent macular erythema confined to the upper eyelid, with associated periorbital edema. File:Dermatomyositis11.jpg|Heliotrope. In patients who have darker skin types (type III - VI skin), heliotrope can be subtle and perceived as inactive or normal, resulting in under-diagnosis in this presenting sign of dermatomyositis. File:Dermatomyositis10.jpg|Heliotrope is often associated with periorbital edema and telangiectasias of the upper eyelids. In the resolution stage, atrophy or dyspigmentation (hypo- or hyperpigmentation) may be apparent. Heliotrope. Subtle erythema and minimal edema involving both upper eyelids, with extension to the lower eyelids. File:Dermatomyositis13.jpg|Malar and facial erythema. Acute onset of confluent macular erythema in a periorbital and malar distribution with extension to the chin in a girl with juvenile dermatomyositis. Note the perioral sparing. File:Dermatomyositis14.jpg|Malar and facial erythema. Striking malar and facial erythema with facial edema and scale represents a recent disease flare in an adult patient with dermatomyositis. File:Dermatomyositis16.jpg|Linear extensor erythema. Confluent erythema of the skin overlying the interphalangeal and extensor tendons of the hand, with extension to the forearm in a patient with dermatomyositis File:Dermatomyositis15.jpg|Linear extensor erythema involving the forearm. This image demonstrates linear violaceous discrete and confluent macules, and erosions secondary to excoriation. Pruritus is an under-recognized symptom of active dermatomyositis. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dermatomyositis」の詳細全文を読む スポンサード リンク
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