Introduction: Gastrointestinal stromal tumour is a nonepithelial tumour, which originates from the submucosal layer of the gastrointestinal wall. It is localized mostly in stomach. Case report: We describe a case study of a 33-year-old patient with Crohn’s disease which affected terminal ileum and colon. After 2 years of taking the therapeutical dose of azathioprine, a 12cm GIST was diagnosed. The patient underwent radical surgical treatment. Half a year after the surgery he is without any significant recurrence of the tumour. Conclusion: The authors used the case report to present the potential risks associated with the immunosuppressive therapy, namely the potential higher incidence of tumours. A slightly increased incidence of non-Hodgkin lymphomas has been proved, however, the increased risk of other tumours has not been proved yet.

        Key words: GIST – immunosuppressive therapy – azathioprine – risks