Staged multi-target therapy for anti-MDA5-positive dermatomyositis-associated rapidly progressive interstitial lung disease: a case report.

Anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis-associated rapidly progressive interstitial lung disease is associated with acute respiratory deterioration and high mortality. A man in his 40s presented with fever, dry cough, progressive dyspnea, mechanic's hand-like lesions and severe hypoxemic respiratory failure. Chest high-resolution computed tomography demonstrated rapidly progressive bilateral ground-glass and reticular opacities. Myositis-specific antibody testing showed strong anti-MDA5 positivity, with concomitant anti-EJ, anti-TIF1γ and anti-Ro52 positivity. Initial intravenous methylprednisolone at 80 mg/day produced limited improvement. Early multi-target escalation included divided-dose methylprednisolone, tofacitinib, short-course intravenous immunoglobulin, Pneumocystis jirovecii prophylaxis and an individualized reduced-dose rituximab regimen consisting of 200 mg followed by three weekly 300-mg infusions. Mycophenolate mofetil was briefly withheld during acute escalation and subsequently resumed for maintenance. Oxygenation improved within 48 h, and serial imaging demonstrated progressive regression of the pulmonary abnormalities. During approximately 6.5 months of follow-up, the patient remained clinically stable without a detected serious opportunistic infection. Because several interventions overlapped and rituximab has a delayed immunological effect, the early response cannot be attributed to rituximab alone. This case illustrates the potential clinical value of staged multi-target treatment adjustment and infection-risk management in severe anti-MDA5-associated rapidly progressive interstitial lung disease.