Immunoglobulin G4-related lung disease mistaken for pulmonary tuberculosis: A case report

Immunoglobulin G4-related disease (IgG4-RD) is a persistent and progressive autoimmune condition marked by inflammation and fibrotic changes in the affected tissues. Cases of IgG4-RD causing pulmonary lesions are relatively rare, and some may be misdiagnosed as pulmonary tuberculosis.

In this report, we present an uncommon instance of IgG4-related lung disease, which was diagnosed through lung tissue biopsy conducted via puncture. A 67-year-old male was hospitalized with a two-month history of cough and sputum production. Chest computed tomography (CT) revealed infiltrative pulmonary tuberculosis in both upper lungs. However, the initial diagnosis was unclear, and the patient received HZRE quadruple therapy for tuberculosis at a local hospital. After 45 days of anti-tuberculosis treatment, the patient's cough and sputum worsened, and he began coughing up blood, prompting transfer to our hospital. Serum tests revealed elevated IgG4 levels. A biopsy of a right lung showed localized fibrous and extensive plasma cell infiltration, with 30-40 IgG4-positive cells per high-power field, and an IgG4/IgG ratio of 40%. These findings led to a diagnosis of IgG4-related lung disease. Following treatment with prednisone and mycophenolate mofetil, follow-up lung CT scans showed significant lesion improvement.

The chest CT findings of IgG4-RD are diverse and nonspecific, often leading to misdiagnosis as pulmonary tuberculosis, especially in primary care settings with limited diagnostic resources. We confirmed the diagnosis of IgG4-related lung disease through histological examination.