title: The association of cryoglobulinaemia with nodules, vasculitis and fibrosing alveolitis in rheumatoid arthritis and their relationship to serum C1q binding activity and rheumatoid factor.
abstract: Two measurements of serum immune complexes, cryoglobulinaemia and 125I-C1q binding, have been performed in patients with severe rheumatoid arthritis (RA) and compared with normal levels. Cryoglobulinaemia was present in 20 out of 28 patients (71%) with extra-articular disease (mean level 17 micrograms/ml) including nodules, digital vasculitis, cutaneous ulcers, rash, neuropathy, lung disease and scleritis, but in none of 32 patients with joint disease alone (uncomplicated RA) (mean level 3 micrograms/ml). Cryoglobulinaemia correlates with, but probably does not antedate, extra-articular disease, and may be useful in predicting morbidity and mortailty in this group of patients. In contrast, serum 125I-Clq binding was raised in patients with uncomplicated RA and those with extra-articular disease, although levels were higher in the latter group. Both tests showed a negative correlation with serum haemolytic complement and a positive correlation with IgM rheumatoid factor although there were some sera with raised levels of rheumatoid factor without cryoglobulinaemia. These results suggest that cryoglobulinaemia is a better test than Clq-binding for demonstrating the presence of circulating immune complexes involved in the pathogenesis of extra-articular lesions.
mesh_terms: D000936:Antigen-Antibody Complex; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000276:immunology*; D001796:Blood Protein Disorders / Q000276:immunology*; D003172:Complement C1 / Q000378:metabolism*; D003450:Cryoglobulins / Q000032:analysis*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000150:complications; D012217:Rheumatoid Factor / Q000378:metabolism*; D012218:Rheumatoid Nodule / Q000150:complications; D014657:Vasculitis / Q000150:complications
chemical_list: D000936:Antigen-Antibody Complex; D003172:Complement C1; D003450:Cryoglobulins; D007136:Immunoglobulins; D012217:Rheumatoid Factor