Hypersensitivity pneumonitis (HP) is an interstitial lung disease (ILD) caused by exposure to a wide variety of organic particles. In this article, we report a rare case of a 44-year-old male patient with cough and shortness of breath for more than 4 years and exacerbation for 1 month. The findings of lung computed tomography (CT) and pathology supported a diagnosis of chronic HP. The patient had a history of ulcerative colitis for 5 years, and used to take salazosulfapyridine more than 4 years since 2013. We organized domestic and foreign experts to discuss the diagnosis and treatment of this case. The final clinical diagnosis was chronic interstitial pneumonia [related to sulfasalazine or inflammatory bowel disease (IBD) itself], pulmonary infections. It is recommended to discontinuation of sulfasalazine and oral administration of glucocorticoids and required long-term follow-up.