Abstract Introduction IgG4-related lung disease (IgG4-RLD) is a rare manifestation of IgG4-related disease, a systemic fibroinflammatory condition that can resemble malignancy or interstitial lung disease. It occurs in approximately 10-14% of IgG4-related disease cases but is seldom isolated to the lungs. Clinical manifestations vary from asymptomatic to chronic cough, dyspnea, hemoptysis, chest discomfort, or fever. Imaging may show pulmonary nodules, ground-glass opacities, mediastinal or hilar lymphadenopathy, pleural thickening, or interstitial changes. Diagnosis relies on characteristic imaging, elevated serum IgG4, and histopathologic evidence of IgG4-positive plasma cell infiltration with fibrosis. Without treatment, progressive fibrosis can cause irreversible lung damage. Early identification and corticosteroid therapy can induce remission and prevent complications. We describe an unusual case of asymptomatic, isolated IgG4-RLD detected incidentally and successfully managed with glucocorticoids. Case Report A 77-year-old woman with a history of asthma and long-standing eosinophilia was hospitalized for recurrent syncope. Evaluation revealed leukocytosis with an absolute eosinophil count of 12.7 ×109/L. Chest CT demonstrated bilateral ground-glass opacities, pulmonary nodules, and mediastinal and hilar lymphadenopathy. She left the hospital against medical advice but returned for outpatient evaluation. On follow-up, she remained asymptomatic with a normal pulmonary exam. Laboratory tests showed positive rheumatoid factor, markedly elevated IgG4 (1,021 mg/dL), elevated IgE (412 IU/mL), low complement C4, and mild proteinuria with hematuria; ANCA and other autoimmune markers were negative. The constellation of radiologic and serologic findings supported a diagnosis of IgG4-related lung disease, which can account for eosinophilia, high IgE, and low complement levels. She was started on prednisone 40 mg daily with a gradual taper. Her eosinophil count and inflammatory markers normalized, and follow-up imaging showed regression of pulmonary abnormalities. She continues low-dose prednisone (5 mg daily, tapering to 2.5 mg) under multidisciplinary follow-up with pulmonology, hematology, and rheumatology. Discussion Although the patient lacked respiratory symptoms, her imaging and serologic profile were characteristic of IgG4-related lung disease. Hypereosinophilic syndrome was considered but is typically not associated with elevated IgG levels. This case underscores the importance of including IgG4-RLD in the differential diagnosis of patients with unexplained eosinophilia, elevated IgE, and abnormal lung imaging. Moreover, a background diagnosis of asthma may obscure the presentation and delay appropriate management. Early recognition and corticosteroid therapy can lead to significant clinical and radiologic improvement, preventing long-term pulmonary damage. This abstract is funded by: None
Carpo et al. (Fri,) studied this question.