D172 - Xanthogranulomatous Pyelonephritis Due to Mycobacterium Kansasii in an Allograft Kidney

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Author Block: T. Stevens, T. Richardson, S. Shawar, Nephrology and Hypertension, Vanderbilt University Medical Center, Nashville, TN
*Purpose: Xanthogranulomatous pyelonephritis (XGP) is a rare and devastating infection of the kidney that leads to extensive inflammation and fibrosis. Diagnosis can be challenging and can occur late in the disease after loss of renal function. Oftentimes, a nephrectomy is required. We herein describe a case of a patient with XGP due to Mycobacterium kansasii in an allograft kidney transplant.
*Methods: A 54 year old male with a history of end stage renal disease due to hypertension status post deceased donor kidney transplant on envarsus, myfortic, and prednisone underwent renal biopsy for acute kidney injury 4 years after transplant. The biopsy showed acute cellular rejection, calcium phosphate crystals, and early transformation to XGP with negative urine cultures. He received intravenous steroids for three days and was started on ciprofloxacin. CT abdomen pelvis noted mild perinephric stranding. His creatinine continued to worsen requiring hemodialysis for uremia. Repeat biopsy showed persistent pyelonephritis. Acid-fast bacilli stain ultimately grew Mycobacterium kansasii. He underwent a nephrectomy of his allograft kidney and was initiated on rifabutin, azithromycin, and ethambutol.
*Results: XGP has previously been called the “great imitator” due to similar signs and symptoms of common ailments such as acute pyelonephritis. It is characterized by invasion of lipid-laden macrophages known as xanthoma cells. While the exact mechanism of disease is unknown, it is thought that urinary obstruction due to nephrolithiasis serves as a nidus for infection and inflammation that leads to profound destruction of the renal parenchyma. Early recognition and treatment of the underlying nephrolithiasis and infection is key to preserving kidney function. It is common for patients to require nephrectomy. Renal transplant is a risk factor for XGP and immunosuppression can lead to atypical infections. This case illustrates the difficulty of diagnosing and managing XGP in kidney transplant.
*Conclusions: XGP is an uncommon and severe infection of the kidney. Diagnosis is challenging and if found late can lead to nephrectomy. Renal transplantation is a risk factor for XGP and in patients with early transformation to XGP with negative urine cultures, atypical infections such as mycobacterium should be considered. A deeper understanding of the pathogenic mechanisms in XGP and targeted biomarkers for quickly identifying pathogens may result in improved outcomes and focused treatment strategies, especially considering the unfavorable prognosis with late diagnosis.