Inflammatory bowel disease (IBD) consisting of Crohn's disease (CD) and ulcerative colitis (UC) are inflammatory conditions affecting the gastrointestinal tract. Infliximab (IFX) is a chimeric anti-tumor necrosis factor antibody used to treat moderate to severe IBD. Eosinophils are commonly found in chronically inflamed tissues in IBD. Peripheral eosinophilia (PE) was previously implicated as a marker of disease severity at diagnosis. The main aim of this study was to investigate whether in IBD patients on IFX, development of PE is associated with adverse outcomes and poor IFX efficacy.
A comprehensive retrospective chart review of IBD patients on IFX (January 2006 to July 2015) treated at a tertiary pediatric IBD center was performed. Data was collected at time specified points over a 24 month period and included demographics, atopy, disease severity, development of PE, human antichimeric antibodies (HACA), infusion reactions, cancer, psoriasis, and loss of clinical response.
One hundred twenty-one IBD patients starting IFX (67 male), mean age of 12.4 years (range 4-22 years old), met inclusion criteria. Of them, 36.3% had ≥1 PE episode (CD: 25 male, 11 female; UC: 6 male, 2 female). Mean absolute eosinophil count (AEC) did not change over time. PE was associated with clinically active disease. Among patients who developed PE, adverse outcomes were not significantly different 
In a cohort of primarily pediatric IBD patients on IFX, PE was associated with clinically active disease; however, PE was not related to increased incidence of adverse outcomes or loss of drug efficacy.