Mesenteric Panniculitis as the First Clinical Manifestation of ANCA-Associated Glomerulonephritis

Introduction: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) comprises a group of autoimmune disorders characterized by inflammation of small- to medium sized blood vessels. AAV often involves multiple organ systems leading to a wide range of clinical presentations. We report a rare case of AAV presenting as mesenteric panniculitis. Case Description: A 63-year-old woman presented to the emergency department of our hospital with a one-month history of abdominal pain. One month before this presentation she was evaluated for similar symptoms. Computed tomography (CT) of the abdomen and pelvis revealed mesenteric fat stranding surrounding multiple subcentimeter lymph nodes, consistent with mesenteric panniculitis. The serum creatinine was elevated to 1.2 mg/dL from her recent baseline Cr of 0.7 mg/dL and a urinalysis demonstrated microscopic hematuria and proteinuria. The patient was discharged with a course of amoxicillin-clavulanate for possible infectious panniculitis. Owing to persistence of her symptoms, she returned one-month later. The patient’s serum Cr was now 5.4 mg/dL Urinalysis again revealed sub-nephrotic range proteinuria and hematuria. Serologic evaluation revealed perinuclear ANCA (p-ANCA) by indirect immunofluorescence (1:320) and elevated MPO IgG (63 AU/mL). Kidney biopsy showed focal necrotizing and diffuse crescentic glomerulonephritis with 69% cellular crescents and 60–70% interstitial fibrosis and tubular atrophy. Electron microscopy demonstrated mesangial and subepithelial immune complex deposits with extensive foot process effacement. These findings were consistent with MPO-ANCA–associated vasculitis with overlapping immune complex features. She was treated with high dose icorticosteroids, followed by induction with cyclophosphamide and initiation of a prednisone taper. Despite the severity of the injury, renal replacement therapy was not required and the patient’s kidney function stabilized. Discussion: This case illustrates a rare presentation of AAV as mesenteric panniculitis. Review of the literature reveals similar cases of patients with panniculitis of the mesentery, breast, or skin later found to have AAV. These cases highlight the high index of suspicion that is needed to prevent delays in diagnosis and should prompt consideration of AAV in patients presenting with panniculitis.