IgG4-related lung disease mimicking COPD: case report and review.

IgG4-RD is a systemic fibroinflammatory condition with a wide range of clinical presentations, including involvement of the respiratory system. While respiratory manifestations are common, IgG4-RD can mimic more prevalent pulmonary conditions, such as asthma or chronic obstructive pulmonary disease (COPD), making diagnosis particularly challenging. In this case report, we describe a patient whose initial symptoms were consistent with COPD, but further investigation revealed that IgG4-RD was the underlying cause. This case highlights the importance of considering IgG4-RD in the differential diagnosis of atypical or treatment-resistant COPD-like presentations to avoid misdiagnosis and ensure timely, appropriate management.