Polyoma BK virus: an emerging opportunistic infectious agent of the human central nervous system.

BK virus, a double-stranded DNA virus, is a member of the Polyomaviridae family which is known to infect humans. Clinical evidence of disease is mostly encountered in immunosuppressed individuals such as AIDS patients or those who undergo renal or bone marrow transplantation where complications associated with BKV infection manifest commonly as a polyomavirus nephropathy or hemorrhagic cystitis, respectively. Recent evidence suggests that in addition to the JC virus (the other member of the same family known to be strongly neurotropic and responsible for the progressive multifocal leukoencephalopathy), BK virus can infect and cause clinically relevant disease in the human central nervous system. In this mini-review, an analysis of the literature is made. A special focus is given to alert clinicians to the possibility of this association during the differential diagnosis of infections of the central nervous system in the immunocompromised host.