Background: IgG4-related disease comprises multiorgan diseases including pulmonary disorders. Though typical lesions are glandular lesions, various lesions are sometimes found in the respiratory system.

Aims: This study aimed to clarify the clinical features of IgG4-related respiratory disease (IgG4-RRD).

Method: The study group of Intractable Diseases, Ministry of Health, Labour and Welfare, Japan, conducted a multicenter retrospective study of IgG4-RRD in Japan and analyzed the collected data.

Results: Data of 115 cases (mean 64.5 yrs. old, m:f 2.6:1) with intrathoracic lesions were collected among which 98% had one or more extrathoracic lesions when diagnosed as IgG4-RRD. The most prevalent symptoms at onset were submandibular gland swelling and cough (each 22.6%). Of the 115 patients, 76 (66%) had a past or present history of airway allergy among whom 18 had asthma, 27 had rhinitis, and the other 31 had both concomitantly.The most common affected organs concomitant with IgG4-RRD at diagnosis were sialadenitis (80% of 115), dacryoadenitis (49%) and pancreatitis (37%). In laboratory data, the mean serum levels of IgG and IgG4 were 2919 mg/dl and 1101 mg/dl, respectively. Hypocomplementemia was observed in 28%. Glucocorticoid (GC) therapy was administered to 94 cases (81.7%), among which over 90% responded well to GC therapy. The prevalence of concomitant malignant disease at diagnosis of IgG4-RRD was 2.6%, and that of malignancy during follow-up (mean 66.4 months) was 7.8%.

Conclusions: Most IgG4-RRD patients had extrathoracic lesions and responded well to GC therapy. Concurrent malignant diseases at time of diagnosis and observed during follow-up of IgG4-RRD should be noted.