BI22 First reported UK case of Kaposi sarcoma in an HIV-negative patient taking pre-exposure prophylaxis

Abstract Kaposi sarcoma (KS) is an angioproliferative disorder that requires infection with human herpesvirus (HHV)-8 for its development. There are four common subtypes: iatrogenic (associated with immunosuppressive medication), classic (affecting older men of Mediterranean and Middle European descent), HIV associated and endemic (arising in parts of Africa in children and young adults). A rare fifth subgroup of KS has been identified in patients who are HIV-seronegative men who have sex with men. In the few previously reported cases of this subgroup, patients have been found to have multiple KS lesions, or the lower limbs are usually affected (Rashidghamat E, Bunker CB, Bower M, Banerjee P. Kaposi sarcoma in HIV-negative men who have sex with men. Br J Dermatol 2014; 171: 1267–8). A single case has been reported in Belgium of an HIV-negative man who was taking pre-exposure prophylaxis (PrEP); however, this patient had multiple lesions affecting his lower limbs, trunk and upper limbs (Hilhorst NT, Devocht B, Verhaeghe E et al. Case series of Kaposi sarcoma in HIV-negative men who have sex with men: potential therapeutic approaches. J Dermatol Res Ther 2024; 10: 127). This case report describes the first instance of a solitary KS lesion presenting on the finger of an HIV-negative man without a history of immunosuppression who has significant risk factors for HHV-8 and HIV infection and is taking PrEP. An otherwise well HIV-negative 44-year-old man from South America taking PrEP and with a history of treated syphilis presented with a 6-month history of a 5-mm papule affecting his left middle finger. This had rapidly increased in size over the last 3 months, was not painful and had not improved with a course of flucloxacillin. Examination of the integument and mucosal sites revealed no other abnormalities. A shave excision revealed a spindle cell neoplasm with an immunohistochemical profile confirming endothelial differentiation. Immunohistochemical staining was positive for HHV-8 and LANA-1, confirming KS. HIV and human T-cell lymphotropic virus tests were repeated and remained negative. This is just the second reported case of KS developing in an immunocompetent, HIV-negative patient on PrEP and the first case in the UK. Furthermore, this is a solitary lesion of the upper limb, which is unique in the literature and highly unusual for KS. This highlights the need for heightened awareness among healthcare providers when diagnosing KS, especially in patients with risk factors for HHV-8 and HIV, even when on PrEP.