PO:24:068 | Case Report: ‘Spontaneous Pneumomediastinum in a Patient with MDA5-Positive Dermatomyositis and Severe Pulmonary Fibrosis’

Carlotta Braga¹, Margherita Rizzo¹, Marta Raschellà¹, Beatrice Maranini¹, Gioacchino Schifino², Aldo Carnevale³, Marcello Govoni¹, Andrea Lo Monaco¹ | ¹Rheumatology Unit, Department of Medical Sciences, University of Ferrara and Azienda Ospedaliero-Universitaria S. Anna Ferrara, Italy; ²Respiratory Medicine Unit, Department of Cardio-Thoracic-Vascular Pathologies, Arcispedale Sant'Anna, Ferrara, Italy; ³Radiology Unit, Department of Translational Medicine, University of Ferrara, Italy

Purpose of the study. Dermatomyositis (DM) is a rare autoimmune inflammatory myopathy. The anti-MDA5-positive subtype represents a distinct and aggressive phenotype, commonly associated with rapidly progressive interstitial lung disease (RP-ILD) and, less frequently, spontaneous pneumomediastinum (SPM), both linked to poor prognosis. This case illustrates the diagnostic and therapeutic challenges in managing such a patient, especially with relevant comorbidities. Material and method: In October 2023, a 45-year-old woman developed classic DM with Gottron’s papules, severe cutaneous vasculitis, muscle weakness, dysphagia, and marked lymphopenia with 250 cells/microL (normal values 1500-5000 cells/microL). Serologic testing was positive for anti-MDA5 and anti-Ro52 antibodies. High-resolution CT (HRCT) in January 2024, performed in the absence of respiratory symptoms, revealed early interstitial changes with ground-glass opacities. Her medical history of vulvar squamous cell carcinoma (July 2022) complicated immunosuppressive management. Initial corticosteroid therapy yielded partial improvement in skin lesions and dysphagia. However, infectious by Listeria monocytogenes meningitis (July 2024) caused a significant complication, delayed the initiation of a more aggressive immunosuppressive therapy and requiring two immunoglobulin (IVIg) cycles for DM control. By October 2024, clinical decline with cutaneous ulcers and severe lymphopenia (80 cells/microL) prompted cyclosporine (CyA) initiation (3 mg/kg/day). Concurrently, imaging revealed worsening ILD with new-onset SPM and subcutaneous emphysema despite the absence of acute respiratory failure. The patient’s condition worsened with massive emphysema extending to the neck and face, requiring hospitalization and placement of bilateral thoracic drains. A multidisciplinary team ultimately approved escalation to rituximab therapy. This combined immunosuppressive regimen led to clinical stabilization, resolution of pneumomediastinum, and gradual improvement in cutaneous symptoms.

Results. SPM is a rare but increasingly recognized complication of anti-MDA5-positive DM, often linked to RP-ILD and poor prognosis. It can occur without respiratory symptoms, complicating the diagnosis. Prognostic markers include cutaneous ulcers, anti-Ro52 antibodies, and persistent lymphopenia. In the present case the management was further complicated by the patient's oncologic and infectious complication. Nevertheless, a stepwise therapeutic approach, beginning with corticosteroids and IVIg, progressing to CyA, and ultimately to rituximab, achieved disease control. Rituximab, supported by growing observational data and emerging trials, appears effective in refractory DM, especially in cases with pulmonary involvement.

Conclusions. This case highlights the complexity of treating anti-MDA5-positive DM, especially in the setting of prior cancer and marked lymphopenia. The clinical severity required timely multidisciplinary management. It supports CyA and rituximab as effective options in refractory cases and underscores the need for greater awareness and further research into this high-risk DM subset.