A case of acute kidney injury due to native kidney BK polyomavirus-associated nephropathy in a human T-lymphotropic virus type 1 carrier

BACKGROUND: BK polyomavirus-associated nephropathy (BKPyVAN) has become a major cause of kidney dysfunction and graft loss in kidney transplant recipients. On rare occasion, polyomavirus has also been known to affect native kidneys of immunocompromised individuals. Only a small number of opportunistic infections have been reported in the carrier phase of human T-lymphotropic virus type 1 (HTLV-1). This is the first reported case of BKPyVAN in native kidneys of an HTLV-1 carrier. CASE PRESENTATION: A 61-year-old man was referred to our hospital from a primary care physician for work-up and treatment of pneumonia. He was diagnosed with Pneumocystis pneumonia and identified as a HTLV-1 carrier who had not yet developed adult T-cell leukemia (ATL). The pneumonia was successfully treated with sulfamethoxazole-trimethoprim. He had never been diagnosed with any kind of kidney dysfunction. Laboratory investigations showed a serum creatinine of 5.3 mg/dL, and urinary sediment showed cells with nuclear enlargement and inclusion bodies suggesting viral infection. The urinary Papanicolaou stain showed inclusions in swollen, ground-glass nuclei, typical of “decoy cells”. Renal biopsy showed degeneration of tubules with epithelial enlargement, vacuolar degeneration, nuclear inclusion bodies, and detachment from the tubular basement membrane. Tubular nuclei showed positive staining positive for simian virus 40 large-T antigen. Polymerase chain reaction tests for BK polyomavirus DNA of both urine and plasma were positive. These findings confirmed a diagnosis of BKPyVAN. Intravenous immunoglobulin therapy did not improve renal function, necessitating maintenance hemodialysis therapy. CONCLUSIONS: BKPyVAN should be considered when acute kidney injury occurs with opportunistic infection. HTLV-1 carriers can develop opportunistic infections even before the onset of ATL.