Digital Ischemia as a Rare Initial Presentation of Myeloperoxidase (MPO)-Anti-neutrophil Cytoplasmic Antibody (ANCA)-Positive Granulomatosis With Polyangiitis: A Case Report

We report a 68-year-old woman with a history of seropositive rheumatoid arthritis, suspected connective tissue disease (CTD)-associated interstitial lung disease, scleromalacia perforans, and osteoporosis who presented with acute ischemia of the left hallux that progressed to involve multiple digits despite therapeutic anticoagulation. Evaluation for cardioembolic, malignant, infectious, and hypercoagulable etiologies was unrevealing.Serologic testing demonstrated elevated rheumatoid factor (660 IU/mL), positive P-ANCA with elevated MPO antibodies (55.2 U), erythrocyte sedimentation rate of 130 mm/hr, C-reactive protein of 5.25 mg/L, and negative proteinase-3 (PR3) antibodies. A skin biopsy of the affected left hallux showed small- and medium-vessel wall inflammation with lymphoplasmacytic and granulomatous infiltrates consistent with GPA. The patient was treated with pulse-dose intravenous methylprednisolone followed by high-dose oral prednisone, which halted the progression of ischemia. Despite this, she required amputation of the left hallux due to dry gangrene after irreversible tissue injury developed. There was no recurrence of ischemia or other systemic vasculitic manifestations after the initiation of rituximab maintenance therapy, with subsequent clinical and serologic remission. This case highlights isolated arterial digital ischemia as a rare but severe manifestation of MPO-ANCA-positive GPA and underscores the importance of considering vasculitis in patients who present with unexplained digital ischemia, particularly when symptoms progress despite anticoagulation, as early immunosuppressive therapy may prevent further vascular injury.