ABSTRACT
IgG4-related disease is characterized by a systemic fibroinflammatory process associated with substantial infiltration by plasma cells with IgG4 in the organs. Our patient presented with pleural effusion, and was diagnosed with IgG4-related lung disease (IgG4-RLD) after he received two doses of the Pfizer COVID-19 vaccine. The patient developed dyspnea and hypoxia 2 weeks after receiving the second dose of the Pfizer COVID-19 vaccine. CT scan revealed left pleural effusion which was drained. However, the effusion recurred requiring thoracoscopic drainage, placement of an indwelling catheter, and decortication with biopsy. IgG4 serum level was 268 mg/dl and pathology revealed pleural fibrosis, lymphoplasmacytic infiltrates, and increased IgG4-positive plasma cells with no malignant cells leading to a diagnosis of IgG4-RLD. Although COVID vaccine-related IgG4-RLD is a novel finding, having a high degree of suspicion following vaccination is always important for early diagnosis and effective treatment.