Background: BK virus nephropathy (BKVN) in native kidneys following lung transplantation is an exceptionally rare occurrence. This case report highlights a unique instance where BKVN developed in a patient's native kidney post lung transplantation, emphasizing its rarity and the importance of considering BKVN in differential diagnoses for patients presenting with acute kidney injury (AKI) after such transplants.

Methods: A 67-year-old male patient who had undergone bilateral lung transplantation 3 years prior presented with worsening creatinine levels following an angiogram. The patient's history included no exposure to toxic medications or other known triggers for kidney disease. The worsening renal function was initially investigated through an angiogram, which was followed by the onset of hematuria and a progressive rise in creatinine levels. To determine the cause of the AKI, a kidney biopsy was performed. The biopsy of the left kidney revealed polyoma nephropathy. Confirmatory tests, including positive staining for simian virus 40 (SV40), confirmed the diagnosis of BKVN in the patient's native kidney.

Conclusions: The occurrence of BKVN in the native kidney following lung transplantation is a rare phenomenon. This case underscores the necessity of considering BKVN in the differential diagnosis of AKI in patients with a history of lung transplantation. Early recognition and diagnosis are crucial for appropriate management and potential modification of immunosuppressive therapy to prevent further kidney damage.