Case Presentation: A 62-year-old male with no significant past medical history presented with a two-month history of diffuse rash, generalized weakness, fever, weight loss, progressive dyspnea and recurrent bronchitis and pneumonia unresponsive to outpatient antibiotics. On admission, he was febrile (102.9 F), hypoxic, tachycardic and hypotensive. On physical exam, he appeared ill with bibasilar crackles, proximal muscle weakness, escharous rash on lower back, gottron’s papules, and excoriations on forearms. Laboratory evaluation showed leukocytosis, with negative autoimmune antibodies including ANA, RF, ESR, CRP, C4, and HLA-B27. Chest CT showed pneumomediastinum with multifocal bilateral ground-glass opacities and interstitial lung abnormalities. MRI of thighs revealed “feathery-like edema” with findings concerning for active myositis. Myositis panel confirmed anti-melanoma differentiation-associated protein 5 (MDA5) antibody positive dermatomyositis (MDA5-DM). The patient was started on steroids and tacrolimus and underwent plasma exchange. Unfortunately, he continued to deteriorate clinically and was placed on extracorporeal membrane oxygenation (ECMO) due to hypoxemia. He was eventually transferred to a lung transplant center due to severe refractory respiratory distress.
Discussion: MDA5-DM is part of a group of diseases that fall under idiopathic inflammatory myopathies. Pathology is thought to be secondary to immune dysregulation including interferon system, T cells, B cells, neutrophils, and macrophage dysfunction often presenting with “feathery-like edema” seen on imaging as in this patient. Classic dermatomyositis is recognized by muscle weakness and arthritis, however, MDA5-DM is unique for its rapidly progressive interstitial lung disease (RP-ILD) and pulmonary complications. It is imperative that hospital medicine is aware of MDA5-DM since many patients will present with non-specific and common symptoms like fatigue, pneumonia, muscle-weakness, or rash which can mask the insidious nature of the disease. Additionally, initial autoimmune screening with routine markers may be negative, which can be misleading, so it is important to pursue further autoimmune testing including a myositis panel when suspicion is high. Unfortunately, as seen with this patient, a delay in diagnosis will lead to RP-ILD refractory to treatment eventually requiring a lung transplant and increasing risk of mortality.
Conclusions: This case is a reminder of the aggressive nature of MDA5-DM with its high risk of RP-ILD, which is a major cause of morbidity and mortality. Early recognition and timely care can be lifesaving since immunosuppression therapy in early stages has better outcomes whereas delayed treatment is often associated with refractory respiratory failure.
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