Primary Sjögren's Syndrome Presenting with Non-Diffuse Membranoproliferative Glomerulonephritis-like Lesions in Cryoglobulinemic Glomerulonephritis: A Case Report

ZhiYu Duan¹GUANGYAN CAI¹FengKun Chen¹Xuanli Tang²Xu Zhang³Ya-li Ren³Yan Song^1*

• ¹First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China
• ²Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang Province, China
• ³First Hospital, Peking University, Beijing, Beijing Municipality, China

Background: In primary membranoproliferative glomerulonephritis (MPGN), mesangial and capillary proliferation manifests as a diffuse, spherical change; in secondary MPGN, lesions are predominantly focal and segmental.Case Presentation: A 52-year-old woman with a 2-year history of primary Sjögren ' s Syndrome (pSS) and no prior renal involvement developed fever, nephrotic syndrome, and acute kidney injury with oliguria after a pulmonary infection. Her highest recorded serum creatinine level was 327.3 µmol/L, and the lowest serum albumin level was 22.1 g/L. Laboratory findings included an antinuclear antibody titer of 1:320, anti-SSA/52KD antibody positivity, complement C3 of 0.468 g/L, complement C4 of 0.0107 g/L, and rheumatoid factor (RF) 678 IU/mL. The highest 24-hour urinary protein quantification reached 9.78 g/24h. After anti-infective treatment, urine output gradually increased, and edema resolved. Cryoglobulin testing showed type II cryoglobulin positivity. Light microscopy revealed MPGN-like lesions in 66.7% of glomeruli and mesangial proliferative glomerulonephritis-like lesions in 25%. Final diagnosis was MPGN.Cyclophosphamide and methylprednisolone were administered. After a 2-year follow-up, the patient's serum creatinine level was 82.1 µmol/L; proteinuria was negative.This case represents the first reported instance of non-diffuse MPGN with cryoglobulinemic GN secondary to pSS. Infection may serve as a key factor in exacerbating cryoglobulinemia and triggering cryoglobulinemic GN onset.