原発性シェーグレン症候群に伴う寡免疫性半月体形成性糸球体腎炎：症例報告

Primary Sjögren syndrome (SS) is a chronic systemic autoimmune disease predominantly characterized by exocrine gland involvement; however, extraglandular manifestations, including renal involvement, may occur and contribute significantly to morbidity. Renal involvement most commonly presents as tubulointerstitial nephritis, while glomerular disease is considerably less frequent. Pauci-immune crescentic glomerulonephritis (GN) is an exceptionally rare renal manifestation of primary SS and is typically associated with antineutrophil cytoplasmic antibody (ANCA)-related vasculitis, although antibody negativity has been described in isolated cases. We report the case of a 30-year-old female with no significant past medical history who presented with hypertensive crisis and rapidly progressive renal dysfunction. Laboratory evaluation revealed acute kidney injury with significant proteinuria. Further evaluation identified sicca symptoms, positive antinuclear antibodies at high titers, and elevated anti-SS-related antigen A antibodies, with normal complement levels and negative ANCAs. Minor salivary gland biopsy confirmed the diagnosis of primary SS. Renal biopsy demonstrated pauci-immune crescentic GN with advanced chronic changes and absence of immune complex deposition on immunofluorescence. The patient was treated with intravenous pulse corticosteroids, resulting in improvement of renal function. This report highlights a rare and atypical form of renal involvement in primary SS and underscores the importance of considering pauci-immune GN in patients with SS presenting with rapidly progressive renal failure, even in the absence of ANCAs. Early recognition and prompt histopathological diagnosis are essential to guide appropriate immunosuppressive therapy and improve renal outcomes.