Acute interstitial nephritis secondary to atheroembolic renal disease as a mimic of ANCA vasculitis

Abstract

Introduction: Atheroembolic renal disease is a rare cause of acute kidney injury (AKI) resulting from the obstruction of renal arteries by cholesterol crystals. It is a multisystemic disease that affects kidneys, skin, gastrointestinal system, and the brain, presenting with livedo reticularis, purpura, nodules, blue toe syndrome, ischemia, uncontrolled hypertension, along with anemia, thrombocytopenia, eosinophilia, elevation of inflammatory markers, proteinuria, and eosinophiluria. In some cases, the presence of antineutrophil cytoplasmic antibodies (ANCA) has been reported, making it mimic ANCA-associated vasculitis.

Case Description: A 66-year-old man with a history of smoking, hypertension, prediabetes, obesity, knee osteoarthritis, dyslipidemia, nephrolithiasis, and chronic kidney disease, experienced a decline in renal function one month after the correction of an abdominal aortic aneurysm with a stent graft. Complex atheromatosis of the aorta was observed during the procedure, and he developed blue toe syndrome postoperatively. Upon admission, the patient was hypertensive and had unintentionally lost 10 kg in the last month. Physical examination revealed a purplish discoloration in several toes and livedo reticularis. Renal ultrasound showed no abnormalities, and urinalysis revealed proteinuria. Ancillary tests revealed positive ANCA measured by ELISA and peripheral eosinophilia. A renal biopsy reported acute interstitial nephritis, interpreted in the clinical context as secondary to atheroembolic renal disease. This condition would explain the positive ANCA, peripheral eosinophilia, skin findings, and histological features. Ultimately, the patient received steroids treatment, leading to improved renal function. To date, the patient has had a satisfactory outcome.

Discussion: Atheroembolic renal disease, occurring in patients with systemic atherosclerosis, can affect renal function acutely, subacutely, or chronically. This disease can mimic small-vessel vasculitis, presenting with similar clinical manifestations and laboratory findings. Several cases in the literature describe patients developing a cholesterol embolism syndrome secondary to arterial procedures or spontaneously, with ANCA positivity and systemic clinical manifestations. These cases highlight the complexity of diagnosing and managing atheroembolic renal disease, emphasizing the need to consider it in the differential diagnosis of small-vessel vasculitis.

Conclusion: In this case, clinical manifestations, laboratory findings, and ANCA positivity suggested vasculitis. However, renal biopsy showed the absence of typical vasculitis findings and signs of acute interstitial nephritis. Furthermore, the clinical presentation and the history of repairing an abdominal aortic aneurysm supported the diagnosis of atheroembolic renal disease. This disease can mimic ANCA-associated vasculitis, underscoring the importance of a careful differential diagnosis.

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