Table 4. Incidence of pulmonary dysfunction in the patient groups.

Normal or pulmonary dysfunction	IgG4-RRD group (n=9), number (%)	IgG4-RDEI group (n=8), number (%)	P value
Normal	0/9 (0)	3/8 (37.5)	0.082
Restrictive ventilatory dysfunction	3/9 (33.3)	2/8 (25.0)	1.000
Obstructive ventilatory dysfunction	2/9 (22.2)	0/8 (0)	0.471
Mixed defect	1/9 (11.1)	0/8 (0)	1.000
Small airway dysfunction	2/9 (22.2)	1/8 (12.5)	1.000
DLCO decrease	9/9 (100)	5/8 (62.5)	0.082
DLCO/VA decrease	5/9 (55.6)	0/8 (0)	0.029*

The incidence of D_LCO/V_A decrease was significantly higher in the IgG4-RRD group than in the IgG4-RDEI group, but there were no other significant differences between the two groups. Both groups of patients showed mainly restrictive ventilatory dysfunction and abnormal diffusing capacity. The ‘pulmonary dysfunction’ refers to the patient had at least one abnormal value in PFTs. Restrictive ventilatory dysfunction means TLC <80% predicted values; obstructive ventilatory dysfunction means FEV1/FVC <70%; mixed defect mean the patient had both restrictive ventilatory dysfunction and obstructive ventilatory dysfunction; small airway dysfunction means the patient had at least two test parameters less than 65% predicted values in MEF50, MEF25 or MMEF75/25 (* indicates significance at the 0.05 level). IgG4-RRD, IgG4-related respiratory disease; IgG4-RDEI, IgG4-related disease extrapulmonary involvement; D_LCO, diffusing capacity of the lung for carbon monoxide; D_LCO/V_A, D_LCO per liter of alveolar volume.