Biopsy-Proven Fungal Pyelonephritis in a Kidney Transplant Recipient

Introduction: Acute pyelonephritis due to bacterial infections is a common cause of acute kidney injury in kidney transplant recipients but fungal pyelonephritis is rare with only a few cases reported. Case Description: A sixty-year-old man with a history of end-stage kidney disease attributed to hypertension who had an unrelated living donor kidney transplant in Iraq, with no known complications presented five months after transplantation with fever, and confusion. He was found to have an acute kidney injury. His urine culture was positive for methicillin-susceptible Staphylococcus aureus and his blood culture was positive for Salmonella. He was treated with empiric ceftriaxone therapy. He had two sessions of hemodialysis due to concern for uremic encephalopathy with improvement in his mental status. Due to a lack of improvement in his kidney function, he had a transplant kidney biopsy that showed fungal forms (Figure 1). He had extensive workup including fungal culture and molecular studies of biopsy tissue, but no organism was identified. His immunosuppression regimen was reduced. He received empiric amphotericin followed by oral isavuconazonium resulting in significant improvement in kidney allograft function and no further need for hemodialysis. Discussion: Fungal pyelonephritis is a rare but serious cause of acute kidney injury in kidney transplant recipients. Observing fungal forms on kidney biopsy is instrumental in the diagnosis. If there is a suspicion of fungal pyelonephritis, for example in patients with systemic fungal infection with acute kidney injury, a kidney biopsy tissue sample should be sent for fungal culture. Our case shows that cases of fungal pyelonephritis in which no specific organism is identified could be successfully treated with empiric amphotericin followed by long-term oral isavuconazonium with close clinical monitoring.Figure 1: Kidney allograft pathology