Critical Crossroads: The Vital Role of Timely Diagnosis in Severe Amyopathic Dermatomyositis

Clinically amyopathic dermatomyositis (CADM) is an uncommon subtype of dermatomyositis (DM) characterized by the typical cutaneous manifestations of DM but without clinical or enzymatic signs of muscle inflammation. We report a case of a 61-year-old woman with a four-week history of dry cough, myalgias, chills, pleuritic chest pain, and worsening shortness of breath. She also had a five-year history of inflammatory polyarthralgia. Upon admission, she was hypoxemic and had subcutaneous emphysema, along with painful papules and erythematous lesions on her fingers. A thoracic computed tomography scan revealed pneumomediastinum and a chronic reticular interstitial pattern. Initially suspected of having COVID-19, laboratory results showed a negative COVID-19 test but positive anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5), leading to a diagnosis of CADM. Treatment with prednisolone and mycophenolate mofetil was initiated, resulting in subsequent clinical improvement. In conclusion, this case of anti-MDA5 positive CADM underscores the diverse range of clinical and radiological findings and the diagnostic challenges they pose. It highlights the importance of anti-MDA5 antibodies as a valuable diagnostic and prognostic tool, given their association with an elevated risk of developing interstitial lung disease (ILD), which may follow a rapidly progressive course and can be further complicated by pneumomediastinum.