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

IgG4-related disease (IgG4-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 IgG4-RD. In this study, we investigated pulmonary function in IgG4-RD patients and evaluated the value of pulmonary function tests (PFTs) in diagnosing IgG4-related respiratory disease (IgG4-RRD).

This was a retrospective study of 17 patients with IgG4-RD. The patients were divided into two groups: IgG4-RRD group and IgG4-related disease extrapulmonary involvement (IgG4-RDEI) group. The PFT results were compared between the two groups.

All patients in the IgG4-RRD group had pulmonary dysfunction. Five of 8 (62.5%) patients in the IgG4-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 IgG4-RRD group had obstructive ventilatory dysfunction. The incidence of diffusing capacity of the lung for carbon monoxide per liter of alveolar volume (D_LCO/V_A) decrease were significantly higher in the IgG4-RRD group than in the IgG4-RDEI group (P=0.029). D_LCO/V_A were significantly higher in the IgG4-RDEI than in the IgG4-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 IgG and IgG subclasses (IgG4, IgG3 and IgG2).

D_LCO/V_A plays an important role for detecting lung involvement in IgG4-RD patients. The patient with high serum IgG may be more prone to respiratory involvement.