The occurrence of Polyomavirus (BK Virus and its Variants) Transplant Nephropathy in Hong Kong and Macau

Abstract

Introduction: BK virus is anephrotrophic polyomavirus that emerges as an important cause of graft dysfunction and failure. The reported incidence of BK virus nephropathy (BKvN) among transplant centers is variable. Our experience of BKvN in a single center is presented. Patients: Renal biopsies archived from 1990 to 2007 in Department of Pathology, Queen Mary Hospital were searched for cases of polyomavirus nephropathy. Selected were 9 graft biopsies from 6 patients. The first patient was from our own hospital and the diagnosis was made in 2005. Two patients were managed in a private hospital in Hong Kong. Biopsies from three patients were referred from a hospital in Macau in 2007. The selected biopsies and clinical features were reviewed. Diagnosis in 5 patients was based on virus-induced cytopathic changes and immunohistochemistry. For one patient, diagnosis was hampered by the negative immunoreactivity of the virus variant to a commercial antibody (Chemicon). The diagnosis was established instead by electron microscopy and detection of viral genome in biopsy tissue. This patient lost the graft kidney 6 months after the initial biopsy. Discussions: Despite the ubiquity of BK virus, we have encountered our first and only case of BKvN of our transplant center two and a half years back. The recent emergence and apparent clustering of cases suggest that some iatrogenic predisposing factors might be involved. The occurrence of virus variants may greatly affects the immunohistochemical detection of viral antigens, which is currently the most important method to diagnose BKvN.