Pneumomediastinum and Pneumopericardium in Rapidly Progressive Interstitial Lung Disease Secondary to Anti‐MDA5 Dermatomyositis

ABSTRACT Anti‐melanoma differentiation associated protein 5 antibody positive dermatomyositis (anti‐MDA5 dermatomyositis) is characterized by rapidly progressive interstitial lung disease and skin involvement with a paucity of muscle involvement. Morbidity and mortality primarily result from lung involvement, which often responds poorly to immunosuppressive treatment. Therapy for Anti‐MDA5 dermatomyositis consists of high‐dose corticosteroid therapy in combination with other immunosuppressive therapies. Recognizing and treating anti‐MDA5 dermatomyositis quickly is imperative to avoid worse outcomes. We report a 74‐year‐old woman who initially presented with a 2‐month history of an erythematous rash over the right greater trochanter, unresponsive to oral flucloxacillin. She later developed acute shortness of breath, haemoptysis, and characteristic dermatomyositis features, including Gottron's papules and a shawl rash. CT pulmonary angiography showed bilateral basal peripheral and perilobular consolidations, with appearances compatible with an organizing pneumonia pattern; no pulmonary embolism was identified. Although her creatinine kinase (CK) was normal, an MRI of both her thighs was requested to assess for muscle inflammation in spite of normal CK levels. This revealed bilateral proximal muscle and subcutaneous oedema. She was diagnosed with dermatomyositis and started on high‐dose prednisolone 40 mg daily while awaiting myositis antibody results and skin biopsy. Three weeks later, she represented with worsening dyspnoea, dysphagia, and chest pain. Repeat CTPA showed new pneumothorax, pneumomediastinum, and pneumopericardium. She received intravenous methylprednisolone followed by intravenous immunoglobulins, but her condition deteriorated, and she died shortly thereafter. Postmortem results confirmed anti‐MDA5 antibody positivity. Anti‐MDA5 dermatomyositis is an important differential in patients with new onset interstitial lung disease, pneumomediastinum, and pneumopericardium due to its rapidly progressive nature. Thorough history and examination for skin manifestations of anti‐MDA5 dermatomyositis is crucial so that a diagnosis can be made promptly and treatment started at the earliest opportunity to avoid development of fatal disease‐related complications and mortality.