Relapse of Rapidly Progressive Interstitial Lung Disease in Anti-MDA5 Antibody-Positive Dermatomyositis Despite Combined Immunosuppression: A Case Report

Background: Anti-melanoma differentiation-associated gene 5 dermatomyositis (MDA5-DM) is a rare autoimmune disease, representing less than 2% of dermatomyositis cases and occurring predominantly in East Asia. It is characterized by hallmark cutaneous features and rapidly progressive interstitial lung disease (RP-ILD), which carries a high six-month mortality risk. Although many patients initially respond to therapy, relapse is uncommon. To date, no case reports have been published from the Philippines. This case adds to the limited literature and highlights the need for vigilant recognition. Case Description: A 50-year-old man with MDA5-DM and prior RP-ILD achieved one year of disease quiescence after plasma exchange, steroid pulses, intravenous cyclophosphamide, and intravenous immunoglobulin. While maintained on prednisone and tacrolimus, he developed a one-month history of fever, cough, exertional dyspnea, and polyarthralgia. Examination showed fever (38[Formula: see text]C), inspiratory crackles, mechanic’s hands, periungual erythema, and hyperpigmented patches over the anterior neck and chest (V-sign) and over the upper back, posterior neck, and shoulders (shawl sign). Investigations demonstrated usual interstitial pneumonia and severely reduced DLCO. Pulmonary tuberculosis was also detected, likely contributing to the relapse; thus, anti-tuberculosis therapy was initiated prior to re-treatment of his underlying autoimmune condition. Discussion: The clinical course of dermatomyositis is heterogeneous. The presence of anti-MDA5 antibodies, associated with rapidly progressive interstitial lung disease, confers a poor prognosis. Although many patients initially respond to glucocorticoids, relapse is common, and sustained control often requires combination therapy with glucocorticoids and other immunosuppressants. In our case, the patient developed an exacerbation after one year of quiescence while receiving prednisone and tacrolimus. Conclusion: Patients with MDA5-DM and RP-ILD may achieve remission with initial therapy, yet relapse can occur despite prior control. These findings support long-term monitoring and individualized management to address the disease’s unpredictable course.