Cryoglobulin-Negative Immune Complex Glomerulonephritis in Sjögren Syndrome

Introduction: Kidney disease in Sjögren’s syndrome (SS) is predominantly tubulointerstitial nephritis, while glomerulonephritis (GN) is rare. Membranoproliferative GN (MPGN) with cryoglobulinemic features has been described within this spectrum. Case Description: A 33-year-old female from Ethiopia with antiphospholipid antibody syndrome, rheumatic heart disease, and SS presented with acute kidney injury (AKI) with creatinine (Cr) 4.8mg/dl (baseline 2 mg/dl), proteinuria (18g/g), hematuria, and volume overload. Serologies revealed low C3, normal C4, positive Ro, and cardiolipin antibodies. Rheumatoid factor (RF), cryoglobulins, antinuclear, anti-dsDNA, and anti-Smith antibodies were negative. Infectious workup revealed latent tuberculosis (TB), needing initiation of isoniazid and rifabutin. Kidney biopsy (Figure 1) showed IgG2 and IgG3 dominant proliferative MPGN with cryoglobulinemic features. She received pulse IV methylprednisolone and subsequent 1mg/kg prednisone for 2 weeks with continued taper. Rituximab was given after 2 weeks of latent TB therapy with improvement in Cr to 2.9 mg/dl and proteinuria to (13g/g). Discussion: SS is the most common cause of non-HCV-related cryoglobulinemic GN with MPGN features. Most present with low C4, positive RF or cryoglobulins, which were absent in our case. Fingerprint deposits are characteristic of lupus or cryoglobulinemia, and lack of serological and clinical evidence of lupus led to the diagnosis of cryoglobulinemic GN related to SS. Anti-CD20 therapies have been successfully used in patients with SS with cryoglobulinemia.