Case Presentation:

A 27 yo male with ulcerative colitis (UC) and childhood asthma presented with a dry cough, fever and weight loss for 6 weeks. One and a half years prior to admission, he was diagnosed with UC for which he was started on oral mesalamine 1.2 g/day. Prior to admission, he visited an outpatient clinic because of shortness of breath. CXR demonstrated b/l upper lobe opacities that subsequently did not respond to a 7 day course of antibiotics. 

Physical examination on admission: Temp 100°F, BP 112/95, HR 126, RR 20, Osat of 94% RA and decreased lung sounds at the bases bilaterally. WBC 14.8K/uL (nl 4.5-10.8) with repeat peripheral eosinophils 1.0K/uL (x<0.9).

CT chest demonstrated dense peripheral opacities in both upper lobes.

Blood, fungal and resp cultures were neg. TB, HIV, Legionella, Histo, Coccidio, Aspergillus and stool O+P tests were neg as well. A transbronchial lung biopsy disclosed increased eosinophils, fibroblastic tissue and foamy macrophage accumulation consistent with eosinophilic pneumonia. There were no viral cytopathic changes, granulomas or malignancy noted. Broncho-alveolar lavage cytology showed increased eosinophils.

Eosinophilic pneumonia secondary to mesalamine was suspected. With the discontinuation of mesalamine and subsequent treatment with steroids, the patient’s symptoms resolved. 


Sulfasalazine is an important drug in the treatment of inflammatory bowel disease (IBD). Unfortunately it is known to cause pneumonitis and rarely, an eosinophilic pneumonia. Mesalamine contains the active ingredient (5-ASA) in Sulfasalazine but without the sulfa moiety, it associated with less side effects and allergic reactions. 

Mesalamine’s common side effects include headache, nausea, abd pain and diarrhea. Only scattered case reports exist regarding Mesalamine-induced lung disease (MILD) and its pathogenesis remains unclear. It appears that in MILD, pulmonary symptoms (usually fever, cough and dyspnea) appear within 5 days to 44 months of drug initiation. It is more common in women than men and is not dose dependent. Also peripheral eosinophilia and CXR findings appear to be variable.


New onset pulmonary disease in patients with ulcerative colitis being treated with mesalamine proves to be a diagnostic challenge. Mesalamine-induced lung disease (MILD) should be considered in any patient that presents with respiratory symptoms on such medication. Medication discontinuation will provide symptom/ disease improvement.