Polyarteritis Nodosa with Bilateral Renal Ischemia Masking as Nephrotic Syndrome in a Diabetic Patient: A Case Report

Introduction: Polyarteritis nodosa (PAN) is a necrotizing vasculitis primarily affecting medium-sized arteries. While PAN may present with mild proteinuria and microhematuria, signs of glomerulonephritis are rare. We report a complex case of PAN in which bilateral renal ischemia accelerated the underlying diabetic kidney disease, hence presenting with nephrotic syndrome and obscuring the diagnosis of PAN. Case Description: A 72-year-old Filipino diabetic female with a four-month history of bilateral pitting edema and worsening hypertension presented to our institution with oliguria and increasing creatinine from 3.2 mg/dL to 4.3 mg/dL (eGFR of 10 mL/min/1.73m2). She was previously managed as rapidly progressive glomerulonephritis at another institution. Workup revealed negative results for ANA, ANCA, hepatitis, and anti-GBM. Abnormal findings include low C3, elevated LDH, nephrotic range proteinuria with UACR of 4744 ug/mg, and hypoalbuminemia. The initial impression was immune complex glomerulonephritis. However, kidney biopsy results were consistent only with those for diabetic kidney disease. She was readmitted for hematochezia, and endoscopy only revealed multiple gastric ulcers. The persistence of gastrointestinal (GI) bleeding prompted CT angiography, which showed irregular narrowing of the distal branches of both renal and superior mesenteric arteries with a beading appearance. Patient developed seizures, and a CT scan of the brain showed acute frontal lobe infarct. With the clinical presentation and angiographic findings, PAN was now highly considered. Repeat MPPT and intravenous cyclophosphamide infusion were given. However, massive GI bleeding persisted, and the patient eventually died. Discussion: The differential diagnosis of PAN is broad, and diagnosis is often delayed due to the wide range of conditions that resemble and complicate the clinical signs. Risk factors for early mortality included older age, renal, CNS, and GI involvement. This case highlights the importance of considering PAN as a possible cause of progressive renal failure, even in patients with nephrotic features, and the potential implications of delayed diagnosis and treatment.