Iatrogenic colorectal Kaposi sarcoma complicating a refractory ulcerative colitis in a human immunodeficiency negative-virus patient

Kaposi sarcoma is a mesenchymal tumor associated to a human herpes virus-8. It often occurs in human immunodeficiency virus-positive subjects. Colorectal localization is rare. We report the case of a colorectal Kaposi sarcoma complicating a refractory ulcerative colitis treated with surgery after the failure of immunomodulator therapy in a human immunodeficiency virus-negative heterosexual man.


Introduction
Kaposi's sarcoma (KS) is a mesenchymal tumor, arising predominantly in the skin but which can affect any organ system.
It's associated to human herpes virus-8 (HHV8) [1,2]. Patients with inflammatory bowel disease, in particular ulcerative colitis (UC), are often treated with immunosuppressive therapy and can develop colorectal KS [3]. We report the case of a human immunodeficiency negative-virus (HIV) man, with a severe refractory UC, who was treated with steroids, azathioprine and infliximab (IFX). Failure of medical treatment indicated surgery. Histological examination of the colon revealed KS. Cytomegalovirus testing was negative too. Detection of Clostridium difficile toxins was not done. Intravenous corticosteroids and parenteral nutrition were prescribed during 1week. At week 5 of corticosteroid therapy, another relapse occurred (7 to 8 stools daily, anemia 6g/dL, ESR 40mm, albumin 17g/L) and we had considered that it was a refractory severe UC. As the patient was reticent to surgery, medical treatment with immunomodulators was indicated.

Patient and observation
Assessment before immunosuppressive therapy was normal. He received blood transfusion, albumin infusion, parenteral nutrition and intravenous corticosteroids (with progressive decreasing doses).

Discussion
There are four clinical variants of KS with distinct clinical and epidemiological characteristics: classic, endemic, acquired immunodeficiency syndrome and iatrogenic [4]. Iatrogenic KS has been described in kidney and liver transplant recipients and also auto-immune diseases [5][6]. KS of gastrointestinal tract is rarely seen in the developed countries. Involvement by KS has been noted in 80% of patients with visceral disease in endemic areas [7]. Case studies have reported colorectal KS associated with inflammatory bowel disease in HIV-negative patients (since until now 11 observations). Most of cases were refractory UC on immunosuppressive therapy [8]. Our patient has received a triple immunosuppression (steroids, azathioprine and infliximab). It's the second case occurring into IFX. The diagnosis is difficult to establish in the absence of skin lesions, as in our patient. Nodular and polypoid lesions are observed in endoscopy and biopsies may fail to sample diagnostic tissue before tumor infiltration of the mucosa [8].
Intraluminal polyps are red or blue, due to high vascular and conjunctive tissue proliferation. Distinction from pseudo-polyps is difficult [9]. Seven months before diagnosis, the colonoscopy showed polypoid lesions, considered as inflammatory pseudo-polyps by the histologist. Immunohistochemistry of HHV-8 is helpful in the histological assessment of the lesions and may demonstrate Page number not for citation purposes 3 infiltration of the mucosa by KS [8]. HHV-8 was positive in our case.
Proctocolectomy associated to immunosuppressor withdrawal is usually effective to treat both UC and KS. After subtotal colectomy and confirmation of KS associated to UC, the patient will undergo proctectomy.

Conclusion
Although it is rare, it is important to consider a concomitant KS in patients with refractory severe ulcerative colitis, on immunosuppressor therapy, independently of HIV status.

Competing interests
There authors declare no competing interest.

Authors' contributions
All authors contributed in this work in ways that conform to ICMJE authorship criteria. All authors read and approved the final manuscript.