Inflammatory bowel disease and lymphoproliferative disorders: the dust is starting to settle

The risk of lymphoproliferative disorders (LDs) has become a major concern for clinicians managing patients with inflammatory bowel disease (IBD). Yet it is difficult to distinguish the possible responsibility of immunosuppressive therapy from the background risk due to the inflammatory disorder itself. LDs are clonal B or T cell proliferation showing considerable heterogeneity and the incidence has increased since the 1970s. The strongest and best-established risk factors for LDs are primary and acquired immunodeficiency (HIV, immunosuppressant), notably via defective immune surveillance of Epstein-Barr virus. In many auto-immune diseases (eg, Sjögren's syndrome), inflammatory diseases (eg, rheumatoid arthritis) or chronic suppuration (chronic pyothorax), the risk of LD is increased. In IBD patients, in general, the risk of LD seems to be similar to or very slightly higher than in the general population. The role of immunosuppressants in lymphomagenesis is difficult to individualise because other factors potentially involved are inter-linked. Concordant data suggest that thiopurine therapy is associated with a moderately increased risk of LD. Data regarding methotrexate are scarce and come from diseases other than IBD but the risk seems low. Data regarding risk of LD in IBD patients receiving anti-tumour necrosis factor alpha (TNFalpha) agents are insufficient at this time, mainly because most of the patients are co-treated with thiopurines. The recently individualised risks of hepatosplenic T cell lymphoma and fatal post-mononucleosis LD, in young male patients with IBD who are co-treated with anti-TNFalpha and thiopurines, and EBV-seronegative IBD males, respectively, are probably low but remain to be better quantified.