A69-06 Pneumocystis Jirovecii Pneumonia in a Patient With Dermatomyositis

Abstract Introduction Dermatomyositis is an immune-mediated myopathy that manifests as various skin lesions, proximal muscle weakness, possible concomitant pulmonary, cardiac, or esophageal involvement. Because treatment often requires long term immunosuppression, patients are at increased risk for opportunistic infections. Pneumocystis jirovecii pneumonia (PJP) is uncommon in those with dermatomyositis but carries a high mortality rate among patients with rheumatic disease, underscoring the importance of a broad differential diagnosis for those presenting with respiratory symptoms. Case report A 66-year-old woman with history of dermatomyositis developed PJP. She was diagnosed with dermatomyositis in 2010 via skin biopsy after presenting with muscle weakness, cutaneous rash, and respiratory symptoms. Notably, she had low maximum inspiratory and expiratory pressures, suggesting neuromuscular weakness putting her at risk for pulmonary complications. She was prescribed immunosuppressive therapy with methotrexate and mycophenolate. In 2025, the patient presented with a month-long progressive dyspnea and productive white cough and was treated with doxycycline and steroids without symptom improvement. Within 2 weeks, she presented to the emergency department with worsening symptoms and hypoxia (88% on room air). Chest radiology showed bilateral hazy opacities suggesting multifocal pneumonia. Computed tomography of the chest showed diffuse patchy ground glass and bandlike areas of consolidation in the lower lobes with peri-lobular and peripheral distribution, suggesting organizing pneumonia. Respiratory, fungal, and acid-fast bacilli cultures were all negative. Urine testing for Legionella and serum testing for Aspergillus were also negative. A bronchoscopy revealed features of organizing pneumonia but PCR analysis of bronchoalveolar aspirate confirmed PJP. Immunosuppression was stopped and was discharged on sulfamethoxazole/ trimethoprim for 21 days and a steroid taper. Her shortness of breath improved and was restarted on immunosuppressive therapy and placed on prophylactic sulfamethoxazole/ trimethoprim. Discussion Patients with dermatomyositis presenting with respiratory symptoms require broad infectious diagnostic testing that includes atypical pathogens, including PJP. Although patients on immunosuppressive therapy with pulmonary risk factors are vulnerable to PJP, diagnosis can be delayed because PJP is not identified through standard cultures. Also, PJP and organizing pneumonia appear similar on imaging, further complicating diagnosis. For our patient, standard cultures were all negative, and imaging suggested organizing pneumonia. However, considering our patient’s history of dermatomyositis with respiratory involvement and immunosuppression, further testing for PJP allowed swift and effective treatment. And although patients with rheumatic disease face high mortality from PJP, clinicians do not routinely administer prophylactic antimicrobial therapy because evidence-based guidelines are lacking, suggesting a need for individual risk assessment. This abstract is funded by: none