Dermatomyositis - Hifukinen (English spelling) Dermatomyositis

Japanese: 皮膚筋炎 - ひふきんえん（英語表記）Dermatomyositis

What is the disease?

The main sites of lesions are the skin and muscles Collagen disease ( Public health center ) Inflammatory symptoms of proximal muscles (muscles close to the center of the body, such as the shoulders, thighs, and upper arms) and skin symptoms may appear simultaneously, or one of them may precede the other. It is most common in children (5-15 years old) and adults (40-60 years old), and about 30% of adults develop malignant tumors and interstitial pneumonia. There is also a form of the disease that shows only skin symptoms, without muscle symptoms.

The cause is unknown.

How symptoms manifest

Characteristic skin symptoms include heliotrope erythema (a reddish purple erythema on the upper eyelid) and Gottron Papule ( Emergency ) (A red rash with a crusty surface of about 2 to 3 mm is clustered on the back of the finger joints, and the rash as a whole is about 1 to 2 cm in size), polymorphous skin atrophy ( Ishku ) (A skin condition that looks dirty at first glance, consisting of a mixture of brown pigmentation, white depigmentation, telangiectasia, and skin atrophy, and is most common on the back.) Nail periphery ( Yes. ) Symptoms include erythema (redness and swelling of the skin around the fingernails) and mechanic's hand (a hard, callus-like rash on the lateral edges of the thumb and index finger).

In addition, there are many other non-specific skin symptoms, such as Raynaud's phenomenon, acrocyanosis, livedo, skin ulcers, calcification, subcutaneous panniculitis, Blisters ( Water ) Muscle symptoms include proximal muscle pain and weakness of varying degrees. cough ( cough ) , During exertion ( Spoon ) It is accompanied by difficulty in breathing.

Testing and diagnosis

Blood tests for antinuclear antibodies, anti-Jo1, etc. are performed. If myositis is present, muscle enzymes such as CK, LDH, and aldolase will be elevated. Skin lesions will require a skin biopsy, and muscle lesions will require an electromyogram and muscle biopsy. In adults, a chest X-ray will be taken, and if interstitial pneumonia is suspected, detailed imaging tests such as CT scans are required. Tests to check for visceral malignant tumors are also required.

Treatment methods

Oral steroids are the first choice. If this is ineffective, pulse therapy (a method of injecting large amounts of steroids) or immunosuppressants are used in combination. For types in which steroids are ineffective, gamma globulin preparations have been reported to be effective. Pulmonary lesions may be accompanied by rapidly progressive interstitial pneumonia, a severe form of pneumonia that is resistant to treatment, in which case early and intensive treatment is necessary.

What to do if you notice an illness

You should immediately see a dermatologist or rheumatologist.

どんな病気か

　皮膚および筋肉を主な病変の場とする膠原病(こうげんびょう)です。近位筋（肩や大腿、上腕など体の中心に近い所の筋肉）の炎症症状と皮膚症状が同時に出る場合と、いずれか一方が先行する場合があります。小児期（5～15歳）と成人（40～60歳）に好発し、成人では約30％で悪性腫瘍と間質性(かんしつせい)肺炎を合併します。筋症状のない、皮膚症状だけの病型もあります。

　原因は不明です。

症状の現れ方

　特徴的皮膚症状としてヘリオトロープ様紅斑（上まぶたのはれぼったい赤紫色の紅斑）、ゴットロン丘疹(きゅうしん)（手指の関節の背面に2～3㎜程度の表面がかさかさして盛り上がった赤い発疹が集まり、全体として1～2㎝程度となる発疹）、多型皮膚萎縮(いしゅく)（茶色の色素沈着、白い色素脱失、毛細血管拡張、皮膚の萎縮が混ざった、一見汚く見える皮膚症状で、背部に多い）、爪囲(そうい)紅斑（爪のまわりの皮膚の赤みとはれ）、機械工の手（母指や示指の側縁のタコのような硬い発疹）があります。

　それ以外にも多くの非特異的皮膚症状として、レイノー症状、アクロチアノーゼ、リベド、皮膚潰瘍、石灰沈着、皮下脂肪織炎、水疱(すいほう)などがあります。筋症状は近位筋の痛みや筋力低下をさまざまな程度で伴います。間質性肺炎では乾いた咳(せき)、労作時(ろうさじ)の呼吸困難を伴います。

検査と診断

　血液では抗核抗体、抗Jo1などを検査します。筋炎がある場合はCK、LDH、アルドラーゼなどの筋逸脱系酵素が上昇します。皮膚病変は皮膚生検、筋病変は筋電図と筋生検を行います、成人では胸部X線写真を撮影し、間質性肺炎が疑われる場合はCTなどの画像精密検査が必要です。内臓悪性腫瘍の合併を調べる検査も必要です。

治療の方法

　ステロイド薬の内服が第一選択です。効果が不十分な時は、パルス療法（ステロイド薬を大量に注射する方法）や免疫抑制薬を併用します。ステロイド薬が効かないタイプでは、ガンマグロブリン製剤の有効性が報告されています。肺病変は急速進行性間質性肺炎という、治療に抵抗する重症肺炎を伴うことがあり、その場合は早期の強力な治療が必要です。