role and clinical implications of ANCA and Its subspecificities in some rheumatic disorders

ABSTRACT

Antineutrophil cytoplasmic antibodies [ANCA] and their sub specificity for target antigens elastase, cathepsin G [CG] and lactoferrin [LF] have been detected in patients with rheumatoid arthritis [RA], systemic lupus erythematosus [SLE] and systemic sclerosis [SSc]. We aimed at finding out the prevalence of ANCA, their target antigens and their clinical implications in Egyptian patients. Serum samples were collected from sixty-one patients. Thirty-two had rheumatoid arthritis [RA], sixteen had systemic lupus erythematosus [SLE] and thirteen had systemic sclerosis [SSc]. Samples were examined for ANCA with the indirect immunofluorescence technique [IIF]. Antibodies directed against elastase, CG and LF were determined using the solid phase enzyme immunometric assay [ELISA]. Statistical studies were used to associate clinical findings to the presence of ANCA sub specificities. In our sample of Egyptian patients, the prevalence of ANCA in RA was 50%, in SLE 42.8% and in SSc it was 55%. The probability of occurrence of antibodies against elastase was 22.3%, CG 13.8% and LF 16.6% in RA patients. The most recognized antigen in SLE patients was anti-elastase 62.5%, CG 25% and LF 18.7%. In RA patients, the presence of anti-elastase antibodies was associated with a long duration of the disease. The presence of CG was associated with the presence of renal affection and erosive changes in X-rays. Skin vasculitic lesions were associated with the presence of LF. In SLE patients, the presence of CG was associated with lupus nephropathy. Positivity for anti-elastase was associated with digital vasculitis and arthropathies. The presence of serositis in SLE patients was not associated with any of the target antigens. In RA patients, serum ANCA sub specificities [anti-elastase, LF] were significantly increased in cases than controls. In SLE patients serum anti-elastase level and anti-Cathepsin G were significantly higher in cases than controls. In SSc patients, only serum anti-elastase was significantly higher in cases than in controls. The prevalence of ANCA in different rheumatic disorders indicates severe disease with increased inflammatory activity. The antibodies directed against target antigens may act as a marker for disease subsets