Predictive factors of renal involvement in cryoglobulinaemia: a retrospective study of 153 patients.

Background: The course of cryoglobulinaemia varies widely, from asymptomatic patients to severe vasculitis syndrome. Renal involvement (RI) is the major prognostic factor, and frequently occurs several years after diagnosis. However, predictive factors for RI are not well known. The aim of our study was to identify RI predictive factors during cryoglobulinaemia.
Methods: We retrospectively reviewed the clinical charts of a consecutive series of 153 patients positive for cryoglobulinaemia in the University Hospital of Lyon (France). RI was defined either histologically or biologically if cryoglobulinaemia was the only possible cause of nephropathy.
Results: Among the 153 positive patients (mean age 55 years, 37% male), cryoglobulinaemia was associated with RI in 45 (29%) patients. Sixty-five percent of patients had Type II cryoglobulinaemia, 28% had Type III and 7% had Type I. Autoimmune diseases were the most common aetiology (48%), followed by infectious diseases (18%) and lymphoproliferative disorders (13%). Membranoproliferative glomerulonephritis was the main histological pattern (93% of the 14 histological analyses). A multivariable logistic regression showed that Type II cryoglobulinaemia, a high serum cryoglobulin concentration, the presence of an IgG kappa monoclonal component and diabetes were independently associated with the risk for developing RI.
Conclusion: We identified several factors predictive of RI in patients with cryoglobulinaemia, which were different from the diagnostic criteria for cryoglobulinaemic vasculitis. This could suggest a specific pathophysiology for RI. We suggest performing an extensive renal monitoring and ensure nephroprotection when a diagnosis of cryoglobulinaemia is made in patients with these predictive factors.