Anti-MDA5 抗體陽性皮肌炎 (anti-melanoma differentiation-associated gene 5 dermatomyositis) 是罕見的自體免疫疾病。根據統計，在亞洲超過8 成以上病人可能發展成快速進展間質性肺病，死亡率高達50%。首選治療為類固醇合併免疫抑制劑，指引建議若對治療無反應可能為難治型個案，建議可增加不同的免疫抑制劑合併治療。

 

本案例為一位46 歲女性，無慢性病史及長期用藥，雙腿出現紅色硬斑擴展至四肢、軀幹。自體抗體檢測MDA5 Ab 3+ 確立診斷。初期僅使用類固醇，因肌肉症狀增加tacrolimus，肺部檢測高度懷疑已進展為間質性肺病，加入rituximab 治療。於第二與三次療程期間，曾因發燒至急診但未住院觀察。第三次療程入院時病人已有間歇性發熱、呼吸困難，診斷為非典型肺炎，使用多種抗生素合併治療。但呼吸症狀持續惡化插管後增加血漿置換、免疫球蛋白，但仍因休克、呼吸衰竭不幸離世。

 

Rituximab 是一種嵌合式的抗CD20 的單株抗體，過去研究顯示可縮小皮疹範圍與改善皮膚潰瘍癒合，並有助於增加用力肺活量及一氧化碳擴散能力，改善間質性肺病。本案例雖使用rituximab 治療，但文獻指出，合併免疫抑制劑比傳統逐步增加藥物更能提高存活率。且感染症是治療過程最常見的併發症，而較高的血清鐵蛋白、低血氧症是影響疾病進展的重要因素，期望透過案例討論與文獻回顧以提供臨床更多資訊。

 

 

Anti-melanoma differentiation-associated gene 5 dermatomyositis (anti-MDA5 DM) is a rare autoimmune disease. Statistics show that over 80% of patients in Asia may develop rapidly progressive interstitial lung disease, with a mortality rate of up to 50%. The first-line treatment involves the use of steroids combined with immunosuppressants. Guidelines suggest that if there is no response to this treatment, the case may be classified as refractory, and it is recommended to incorporate additional immunosuppressants in combination therapy. 

 

We present the case of a 46-year-old woman with no history of chronic illness or long-term medication use, who developed red, hard plaques on her legs that spread to her limbs and trunk. She was diagnosed with MDA5 Ab 3+ autoantibodies. Initial treatment with steroids was supplemented with tacrolimus due to worsening muscle symptoms. Subsequent lung tests highly suggested the progression to interstitial lung disease, prompting the addition of rituximab to her treatment regimen. During the second and third courses of treatment, the patient experienced fever and visited the emergency department but was not admitted for observation. Upon admission for the third treatment, she presented with intermittent fever and breathing difficulties and was diagnosed with atypical pneumonia, which was treated with multiple antibiotics. Despite additional interventions, including plasma exchange and immunoglobulin therapy after intubation, the patient unfortunately passed away due to shock and respiratory failure. 

 

Rituximab, a chimeric anti-CD20 monoclonal antibody, has been shown in previous studies to reduce the size of skin rashes, promote the healing of skin ulcers, increase forced vital capacity and carbon monoxide diffusing capacity, and improve interstitial lung disease. Although rituximab was administered in this case, literature suggests that combining immunosuppressants is more effective at improving survival rates than the traditional stepwise escalation of medications. Infections are the most common complications during treatment, and higher serum ferritin levels and hypoxia are key factors influencing disease progression. Through this case discussion and literature review, we hope to provide additional clinical insights.

 

 

Submitted for publication: 2024.1.15; Accepted for publication: 2024.6.11