An observational study on lupus nephritis combined with cryoglobulinemia.

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus (SLE), and cryoglobulinemia is relatively common in SLE, with both conditions potentially leading to kidney injury. This study aimed to describe the clinical features of LN with cryoglobulinemia and explore whether more aggressive treatment should be considered in such cases. This retrospective study at Peking University First Hospital (2006-2024) analyzed 127 LN patients screened for cryoglobulinemia to assess its prevalence, clinical impact, and treatment implications. 63.8% of LN patients showed concurrent cryoglobulinemia. Patients with cryoglobulinemia showed more severe hypocomplementemia (p = 0.002) and leukocyturia (p = 0.018). Type II cryoglobulinemia (n = 9) showed higher serum creatinine (p = 0.025) and IgM (p = 0.030) versus those with type III (n = 70). 13 out of 81 patients with cryoglobulinemia exhibited ultrastructural changes on electron microscopy. The average follow-up was 58.0 (39.0, 87.0) months; 58.0% achieved complete renal response (CRR), 25.9% attained partial renal response (PRR), and 16.1% had no renal response. After propensity score matching (PSM), patients with cryoglobulinemia who received plasma exchange (PE) therapy showed no statistically significant difference in renal remission compared to those who did not undergo PE therapy (p = 1.000). Cox regression showed that cryoglobulinemia was not an independent risk factor of poor renal outcomes in LN (HR = 1.004, 95% CI [0.498-2.021], p = 0.992). Cryoglobulinemia is prevalent and was not an independent risk factor for renal prognosis in LN. PE may not provide additional benefits in LN patients with cryoglobulinemia.