Abstract IgG4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder characterized by lymphoplasmacytic infiltrates rich in IgG4-positive CD19+ B cells, which promote fibrosis through cytokine and T-cell activation therefore creating a distinctive histopathologic feature of storiform fibrosis Although IgG4-related disease (IgG4-RD) most commonly affects the pancreas and biliary tract, it can involve nearly any organ system, including the lungs. We present a rare case of IgG4-related pulmonary disease manifesting as recurrent inflammatory pseudotumor. A 50-year-old male with a history of incarceration and prior mold exposure presented with chronic cough and was found to have a left upper lobe (LUL) mass on chest X-ray. Computed tomography (CT)-guided biopsies and bronchoalveolar lavage were nondiagnostic, and cultures were negative. Positron emission tomography (PET) demonstrated intense fluorodeoxyglucose (FDG) uptake concerning for malignancy. This prompted video-assisted thoracoscopic surgery (VATS) with wedge resection revealing mixed inflammation and dense collagenous fibrosis consistent with inflammatory pseudotumor, with superimposed aspergilloma, requiring left lower lobectomy, and later completion pneumonectomy for recurrent symptoms. A concurrent biopsy of a retroperitoneal lesion demonstrated fibroblastic proliferation with mixed inflammatory infiltrate. A follow-up CT chest demonstrated a new right middle lobe (RML) nodule, and subsequent endobronchial ultrasound (EBUS) biopsy showed chronic inflammation with a dense plasma cell infiltrate, negative for malignancy. After being lost to follow-up for two years, a CT chest showed a 4.5 × 4.2 cm RML mass, suspicious for recurrent pseudotumor, but surgery was deferred, and the patient was initiated on prednisone 40 mg daily with a prolonged taper for presumed IgG4-RD. This case highlights the diagnostic challenges of IgG4-related pulmonary disease. Histopathologic analysis remains the gold standard for IgG4-RD diagnosis, as serum IgG4 may be normal in up to 30% of patients. In some instances, even after multiple site biopsies, a definitive diagnosis may rely on observing a clinical response to treatment. Glucocorticoids are first-line therapy, with immunomodulators such as azathioprine, mycophenolate mofetil, or methotrexate used as second-line or steroid-sparing agents. B-cell-depleting agents like rituximab or inebilizumab are effective for refractory or relapsing cases. This abstract is funded by: none
Hakim et al. (Fri,) studied this question.