Pulmonary function tests findings and their diagnostic value in patients with IgG4-related disease.

Background: I(g)G4-related disease (I(g)G4-RD) is an immune-mediated fibroinflammatory disorder that can affect most organs. To date, there have been no detailed assessments of pulmonary function in patients with I(g)G4-RD. In this study, we investigated pulmonary function in I(g)G4-RD patients and evaluated the value of pulmonary function tests (PFTs) in diagnosing I(g)G4-related respiratory disease (I(g)G4-RRD). Methods: This was a retrospective study of 17 patients with I(g)G4-RD. The patients were divided into two groups: I(g)G4-RRD group and I(g)G4-related disease extrapulmonary involvement (I(g)G4-RDEI) group. The PFT results were compared between the two groups. Results: All patients in the I(g)G4-RRD group had pulmonary dysfunction. Five of 8 (62.5%) patients in the I(g)G4-RDEI group had pulmonary dysfunction, despite having normal thoracic computed tomography scans and no respiratory symptoms. Patients in both groups showed restrictive ventilatory dysfunction and abnormal diffusing capacity, and two patients in the I(g)G4-RRD group had obstructive ventilatory dysfunction. The incidence of diffusing capacity of the lung for carbon monoxide per liter of alveolar volume (DLCO/V-A) decrease were significantly higher in the I(g)G4-RRD group than in the I(g)G4-RDEI group (P= 0.029). DLCO/VA were significantly higher in the I(g)G4-RDEI than in the I(g)G4-RRD group (P= 0.044), but otherwise, there were no significant differences. We report the first finding of a negative correlation between pulmonary diffusing capacity and total serum concentrations of I(g)G and I(g)G subclasses (I(g)G4, I(g)G3 and I(g)G2). Conclusions: DLCO/VA plays an important role for detecting lung involvement in I(g)G4-RD patients. The patient with high serum I(g)G may be more prone to respiratory involvement.