A case of recurrent progressive multifocal leukoencephalopathy after human stem cell transplant, with detection of John Cunningham virus and human herpesvirus 6 on cerebrospinal fluid, treated with Mirtazapine, Olanzapine and Foscarnet.

We reported the case of a John Cunningham virus (JCV) and human herpesvirus 6 (HHV-6) mediated progressive multifocal leukoencephalopathy (PML) after human stem cell transplant, reactivated 6 months later in absence of immunosuppressive therapy, successfully treated with anti-5HT2A receptors agents and antiviral therapy. Few cases of JCV and HHV-6 coinfection associated PML are described in literature and the role of HHV-6 in the pathogenesis and prognosis of PML is not completely clear. Our case suggests that, in a possible PML, the research of HHV-6 and JCV should be always performed on cerebrospinal fluid (CSF) and on blood samples and in case of detection of HHV-6 DNA a chromosomally integrated human herpesvirus 6(ciHHV-6) should be excluded. Furthermore we recommend to start an appropriate therapy with antiviral and anti-5HT2A receptors agents in case of possible PML due to JCV and HHV-6 coinfection.