MPO-ANCA +AAV MANIFESTING AS GCA: A CASE REPORT

Summary: Background: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are inflammatory disorders affecting small vessels, and include granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (EGPA). GPA is associated with Myeloperoxidase-ANCA (MPO-ANCA) and proteinase 3 (PR3-ANCA), and typically presents with sinonasal disease as well as lower respiratory tract involvement. We focus on a unique case of MPO and PR3-ANCA positive AAV initially resembling giant cell arteritis (GCA). Case Presentation: A 66-year-old female with a history of arthritis, hypertension, and obstructive sleep apnea presented to the ED with sudden vision loss in her right eye and scalp tenderness associated with fevers, cough and congestion lasting one week. Episodes of coughing and achiness, partially improved by antibiotics and steroids, as well as a history of sensorineural hearing loss and mouth sores were reported on ROS. CXR revealed masses, and further evaluation with CT chest showed extensive multiple pulmonary nodules. PET scans showed extensive lymphadenopathy. Bronchoscopy with biopsy showed features of vasculitis and a plasmacytic infiltrate with elevated IgG4+ cells. In the ED, ESR and CRP were elevated to 95 and 65.7, respectively. Suspecting giant cell arteritis (GCA), high-dose steroids were administered, however temporal artery biopsy (TAB) was inconclusive. Further lab tests showed positive ANA (speckled pattern, 1:160), c-ANCA (titer of 1:320), MPO >8, and positive RF. With suspicion of MPO-ANCA positive AAV based on history, the patient received treatment with Avacopan and Rituximab. Upon re-evaluation in the clinic, she reported symptom improvement and had tapered her Prednisone dose to 5 mg daily. Discussion: AAV may exhibit GCA-like manifestations, and evidence of overlap dates back to the 1970s1. In a recent case-control study with 50 presumed GCA patients, 66% presented with atypical symptoms, including ear, nose, and throat as well as renal, pulmonary and neurologic involvement. ANCAs were positive in 88% however diagnosis was delayed in most patients by an average of 15 months.2 Furthermore, TAB findings are typically inconclusive in distinguishing these disorders3. This case highlights that ANCA testing should be considered in atypical GCA cases. Overall, the diverse clinical presentations pose diagnostic challenges and delay treatment, impacting the prognosis. Conclusion: This case highlights that ANCA testing should be considered in atypical GCA cases. The diverse clinical presentations can pose diagnostic challenges and delay treatment, impacting the prognosis.