Lymphopenia in Inflammatory Bowel Disease Patients on Immunosuppressive Medications

Abstract

Azathioprine and 6-mercaptopurine (AZA/6MP) are effective immunosuppressives used for the treatment of inflammatory bowel disease. The optimal strategy for monitoring therapeutic efficacy and adequate immunosuppression remains to be defined. White blood cell count, mean corpuscle volume (MCV), and 6-mercaptopurine metabolites (6TGN, 6MMP) have all been suggested as potential parameters to monitor efficacy and safety. However, immunomodulators target lymphocytes specifically rather than leukocytes overall; little data is available on the relationship between lymphocytes and immunomodulators in IBD. This study evaluates the incidence of lymphopenia with immunosuppressive use, and correlates metabolite levels (6TGN and 6MMP) with leukocyte, lymphocyte, and MCV levels in IBD patients treated with AZA/6MP. Medical records of 125 adult IBD patients were analyzed based on the use of AZA/6MP, blood counts, and mercaptopurine metabolites 6TGN and 6MMP. Forty three percent of patients taking AZA/6MP developed lymphopenia. Of those with lymphopenia, only 11% had leukopenia. A low but statistically significant correlation of r = -0.3 (p=0.04) for 6TGN to leukocyte counts as well as to MCV levels was found. No correlation between 6TGN levels and lymphocyte counts was noted. This analysis shows that not only leukocyte counts but lymphocyte counts should be monitored closely in patients on these immunosuppressives. Metabolite markers do not provide information regarding who will develop lymphopenia. Consequences of lymphopenia such as opportunistic infections need to be discussed with patients prior to starting this type of therapy.