Abstract Introduction Twenty-six years old male with history of ulcerative colitis (UC) and type 2 diabetes mellitus developed subacute interstitial pneumonia secondary to mesalamine use. Case Description The patient presented to the emergency department for an UC flare, with multiple episodes of hematochezia, abdominal pain, weight loss, and associated progressive shortness of breath, pleuritic chest pain, and dry cough. Respiratory symptoms started 2 months prior to admission, at the time when mesalamine was introduced. On encounter, vital signs were significant for tachycardia. Complete blood count showed leukocytosis of 18,000 with neutrophil predominance, and eosinophilia above 3000. Chest x-ray revealed a left apical peripheral opacity. Chest computed tomography angiography showed bilateral, peripheral, upper lobe consolidations. Initial work up for his respiratory symptoms contemplated community-acquired pneumonia (CAP), eosinophilic pneumonia, and drug-induced pneumonitis as main differential diagnoses. Patient was treated empirically for CAP and with corticosteroids for his UC flare, while holding mesalamine. An extensive infectious workup was obtained with negative results. Respiratory symptoms gradually improved, but eosinophilia persisted for several days. A bronchoscopy with bronchoalveolar lavage was performed with no major findings. It’s leukocyte differential had 34% neutrophils, 13% lymphocytes, 5% eosinophils, and 48% monocytes. Given the negative infectious workup, eosinophilia, and the timeline of respiratory symptoms developing after starting mesalamine, it was determined that they were induced by this medication, as a diagnosis of exclusion. He completed a 5-day course of empiric antibiotics for CAP and was discharged on a steroid taper, with plans to start biologics to substitute mesalamine. Discussion Mesalamine is a first-line therapy for the treatment of mild to moderate inflammatory bowel disease (IBD). It is usually well-tolerated, but has the rare potential of pulmonary side effects, such as drug-induced pneumonitis, and eosinophilic and interstitial pneumonia. Given the rarity of it’s side effects, it tends to be often misdiagnosed as CAP or asthma, depending on its clinical presentation. Laboratory findings tend to show leukocytosis with eosinophilia. Imaging findings are non-specific, but, based on prior case reports, the presence of bilateral, peripheral, upper lobe predominant consolidations are highly suggestive. It is usually a diagnosis of exclusion, with eosinophilia, abnormal radiologic findings, and history of improvement after discontinuation mesalamine being supportive findings. Conclusion In patients with IBD treated with mesalamine, unexplained respiratory symptoms should be considered as a potential complication of therapy. This abstract is funded by: None
Licerio et al. (Fri,) studied this question.