Human herpesvirus 8-associated colonic Kaposi's sarcoma during vedolizumab treatment in ulcerative colitis: a case report and review of the literature.

BACKGROUND: Kaposi's sarcoma (KS) is a rare vascular tumor associated with human herpesvirus (HHV)-8 infection. One of the variants of KS is defined iatrogenic and is overall reported in transplanted patient but also, although less frequently, in patients treated with long-standing immunosuppressive therapy, such as in inflammatory bowel disease including ulcerative colitis and Crohn's disease. CASE PRESENTATION: Herein, we report the first case of KS in a human immunodeficiency virus (HIV)-negative 47-year old male with UC after treatment with the α4-ß7 integrin inhibitor vedolizumab (VDZ). The patient underwent to colectomy for a medical refractory disease and the histological examination of the surgical specimen showed the typical findings of KS together with the HHV-8 positivity. The patient achieved a good health status, without any sign of disease recurrence. CONCLUSIONS: In the present case, we can assume that VDZ may have promoted the reactivation of a latent HHV-8 infection endowed with oncogenic potentialities and, in turn, the onset of KS. We also briefly reviewed all the cases of KS in HIV-negative patients with inflammatory bowel disease.