Use of case reports and the Adverse Event Reporting System in systematic reviews: overcoming barriers to assess the link between Crohn's disease medications and hepatosplenic T-cell lymphoma.

To identify demographic and clinical characteristics associated with cases of hepatosplenic T-cell lymphoma (HSTCL) in patients with Crohn's disease, and to assess strength of evidence for a causal relationship between medications and HSTCL in Crohn's disease. We identified cases of HSTCL in Crohn's disease in studies included in a comparative effectiveness review of Crohn's disease medications, through a separate search of PubMed and Embase for published case reports, and from the Food and Drug Administration (FDA) Adverse Event Reporting System (AERS). We used three causality assessment tools to evaluate the relationship between medication exposure and HSTCL. We found 37 unique cases of HSTCL in patients with Crohn's disease. Six cases were unique to the published literature and nine were unique to AERS. Cases were typically young (