A 69-year-old man was diagnosed with immunoglobulin (Ig) G4-related disease (IgG4-RD) at 62 years old. At that time, he had high serum IgG4 levels and bilateral submandibular gland swelling on CT; thus, a gland biopsy was performed. Because a reticular shadow was found on chest CT, a lung surgical biopsy was also performed. The specimens revealed usual interstitial pneumonia (UIP) pattern interstitial pneumonia with some IgG4-positive cells. The patient was subsequently followed up without treatment. His forced vital capacity and radiological findings progressively deteriorated, consistent with UIP pattern interstitial lung disease but different from a lung lesion of IgG4-RD.
Keywords: immunoglobulin (Ig) G4; immunoglobulin (Ig) G4-related disease (IgG4-RD); interstitial pneumonia; progressive fibrosing; usual interstitial pneumonia (UIP).