[A CASE OF IgG4-RELATED DISEASE WITH CONFIRMED RESPONSE TO DUPILUMAB BY SMALL SALIVARY GLAND BIOPSY].

A 71-year-old man was referred to our department due to a cough that occurred one year after surgery for papillary duodenal cancer. We clinically diagnosed the patient with bronchial asthma, with an increase in peripheral blood eosinophil count, exhaled NO, and IgE and obstructive ventilation disorders based on pulmonary function tests. Fluticasone-vilanterol was introduced, but there was little improvement in the cough. We suspected bronchial asthma complicated by IgG4-related disease due to the high serum IgG4 levels and diagnosed the patient with IgG4-related disease through a pancreatic tissue stain of a previously resected duodenal papillectomy section. When dupilumab was initiated for bronchial asthma complicated by IgG4-related disease, the cough resolved. In addition, serum IgG4 levels decreased after the initiation of dupilumab treatment, and a decrease in IgG4-positive plasma cells was observed on small salivary gland biopsy. Thus, the treatment of inhaled steroid-resistant bronchial asthma with dupilumab can also improve IgG4-related disease, and we confirmed a decrease in IgG4-positive plasma cells in the small salivary glands.