A40-32 IgG4-Related Lung Disease: A Rare and Overlooked Cause of Progressive Dyspnea

Abstract Introduction The incidence of IgG4-related disease is 1.2-1.4 per 100,000 person-years, with IgG4-related lung disease being rarer, occurring in only about 10% of cases. We present a case of a 73-year-old man with persistent dyspnea who was ultimately diagnosed with IgG4-related lung disease after extensive evaluation. Case description A 73-year-old man with a history of prostate cancer on observation protocol, chronic obstructive pulmonary disease, coronary artery disease status post percutaneous coronary intervention presented with sudden-onset exertional shortness of breath. A stress test revealed abnormal myocardial perfusion with an inferior wall scar and minimal peri-infarct ischemia, consistent with known right coronary artery occlusion. Despite optimal medical management and subsequent drug eluting stent placement in the mid-LAD, his dyspnea persisted. CT angiography of the chest was done which showed mediastinal lymphadenopathy with emphysematous changes and dependent atelectasis. Pulmonary function testing demonstrated severe obstructive lung disease with air trapping and diffusion impairment, without bronchodilator response. Laboratory workup showed normal inflammatory markers and immunoglobulin levels, with mild monocytosis on flow cytometry. Given mediastinal lymphadenopathy and history of prostate cancer and smoking, PET imaging was performed, revealing hypermetabolic mediastinal lymph nodes. Subsequent CT imaging showed new left lung consolidations suspicious for pneumonia, along with bilateral pulmonary nodules and persistent mediastinal lymphadenopathy. Despite antibiotic therapy, repeat imaging showed worsening multifocal infiltrates, raising concern for malignancy or cryptogenic organizing pneumonia. A CT-guided left lung core biopsy demonstrated fibrosis, thick-walled vessels, and increased polytypic plasma cells. Total IgG was elevated at 1693 mg/dL, IgG4 at 166.9mg/dL and IgE markedly elevated at 12,150 kU/L. The patient was started on a slow taper of oral prednisone, beginning at 40 mg daily, under oncology supervision. Follow-up imaging showed marked improvement in lung consolidations and lymphadenopathy, with significant symptomatic improvement in exertional dyspnea and reduced oxygen requirements. Conclusion This case highlights the rarity of IgG4-related lung disease and its potential to mimic other pulmonary or malignant conditions. It underscores the importance of considering IgG4-related disease in patients with unexplained pulmonary infiltrates or mediastinal lymphadenopathy who fail to respond to conventional management. Early recognition and corticosteroid therapy can lead to significant radiologic and symptomatic improvement. Before and after treatment: CT chest showing multifocal consolidations at presentation and near complete resolution following cortoosteroid therapy This abstract is funded by: None