Merkel cell polyomavirus infection and Merkel cell carcinoma in HIV-positive individuals

Purpose of review Merkel cell polyomavirus (MCPyV) was recently discovered in Merkel cell carcinoma (MCC), an aggressive nonmelanoma skin tumour. MCC incidence has been rising in the last decades. Immunocompromised individuals such as HIV-infected patients have an increased risk for MCC development. Recent findings MCPyV is found - mostly integrated into the host genome - in approximately 80% of MCC. The causal role of MCPyV in MCC development has been corroborated by several recent studies. Cutaneous MCPyV infection is acquired early in life and is widespread in the general population. In HIV-positive patients, MCPyV-DNA has been detected on the skin, on oral and anogenital mucosa, and in plucked eyebrow-hairs. Compared with healthy controls, MCPyV prevalence is increased in HIV-infected individuals and severe HIV-related immunosuppression is associated with elevated cutaneous MCPyV-DNA loads. This could explain the increased MCC risk found in HIV-infected individuals. MCC in HIV-infected patients occurs at a relatively young age and frequently on sites not exposed to sunlight. Summary Guidelines for screening and early detection of MCC should be developed for HIV-positive patients. Future studies should evaluate changes in MCC incidence rates in HIV-infected individuals and analyse the effect of immune restoration by (early) antiretroviral therapy on MCC incidence and on cutaneous MCPyV load.