Intravenous Human Immunoglobulin in the Treatment of BK Virus Nephropathy in Kidney Transplant: A Case Report

The BK virus infection is common in the immunocompetent population and is asymptomatic in the majority of cases. However, in renal transplant patients, reactivation and replication can occur, leading to the development of BK virus-associated nephropathy (BKVN), which is associated with renal injury and graft loss. The objective of this case report was to demonstrate a case of BKVN that showed a good response to the use of human immunoglobulin. A 37-year-old man who underwent a second transplant received rabbit-derived antithymocyte human immunoglobulin at a dose of 6 mg/kg intravenously as induction immunosuppressive therapy, and maintenance therapy with tacrolimus, prednisone, and mycophenolate sodium (MFS). At 3 months post-transplant, he presented sustained BK virus viremia (70,000-100,000 copies/mL), leading to a reduction in the dose of MFS and tacrolimus. A biopsy diagnosed BKVN class 2/B2, and viremia increased to over 1 million copies/mL at 22 months, prompting the discontinuation of tacrolimus without response. Intravenous human immunoglobulin (IVIG) was administered at 2 g/kg at 22 months and again at 33 months, with viremia peaking at 2 million copies 3 months later. However, it steadily declined to 5500 copies/mL at 52 months post-transplant. Currently, the only proven therapy for BKVN is the reduction of immunosuppression. However, in patients who do not respond, IVIG is considered as an option, with good results demonstrated in case reports, as shown here. Nevertheless, the data are based on case reports or case series, and the development of controlled clinical trials is necessary for confirmation of the efficacy.