To determine the prevalence and nature of cryoglobulins in 122 patients with systemic lupus erythematosus (SLE) and identify the clinical and immunologic features related to their presence.
In a cross-sectional study, we investigated 122 consecutive patients (106 women and 16 men) with SLE who fulfilled the 1982 revised criteria of the American College of Rheumatology for the classification of SLE. All patients had documented medical histories and underwent a medical interview as well as a routine general physical examination by a qualified internist, and their clinical and serologic characteristics were collected on a protocol form. Serum samples were obtained at 37 degrees C, and cryoglobulinemia was estimated by centrifugation at 4 degrees C after incubation for 7 days in all patients. The type of cryoglobulinemia was identified by agarose gel electrophoresis and immunofixation.
Cryoglobulins were detected in the sera of 31 SLE patients (25%): 20 patients (65%) had a cryocrit lower than 1%, 8 (26%) had percentages ranging between 1% and 5%, and only 3 patients (9%) had a cryocrit over 5%. Only cutaneous vasculitis (39% v 16%; P = .01) was more prevalent in patients with than in those without cryoglobulins. Rheumatoid factor (RF) (42% v 15%; P = .002) and low CH50 levels (84% v 49%; P <.001) were more prevalent in SLE patients with cryoglobulins. Hepatitis C virus (HCV) infection was investigated in 24 of the 31 cryoglobulinemic SLE patients and was detected in 5 (21%). In comparison, 4 (5%) of the 75 noncryoglobulinemic SLE patients studied were positive (P = 0.035; odds ratio, 4.67). Patients with a cryocrit greater than 1% showed a higher frequency of HCV infection than those with a cryocrit less than or equal to 1% (46% v 0%, P = .01).
Cutaneous vasculitis, RF, hypocomplementemia, and HCV infection were associated with cryoglobulins in SLE patients. Testing for HCV infection is therefore recommended for patients with SLE and cryoglobulinemia to identify this subset of patients for prognostic and therapeutic reasons.