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Anti-neutrophil cytoplasmic antibody (ANCA) are produced against lysozomal constituents and primary granules of myeloid cells (Neutrophiles & monocytes) in some rheumatic diseases and wegner’s granulomtosis (WG). This antibodies not only may related to onset of vasculitis lesions, but also have a valuable diagnostic tool, thus, first we tired to evaluated the prevalence of this antibodies in 65 serum of patients with RA and 42 serum of patients with SLE. By using of indirect immunoflourescence assay (IFA), two staining patterns are recognized: Cytoplasmic (C-ANCA) pattern which in 80% of results from anti-PR3, and prenuclear (P-ANCA) pattern, which can result from any antibody directed to myeloperoxidase (MPO), cathepsin G (CG) lactoferrin (LF), elastsae (HLE) and lysozyme (LZ). The sensitivity and specificity for SLE from 1:128 serum dilution was 8% and 85.1% respectively, and for RA from 1:16 dilution was 32.2% and 87.5% respectively. Of the 19 SLE, ANCA positive patients 18 (94.7%) had P-ANCA and 1 patient (5.3%) had C-ANCA and of the 23 RA, ANCA positive patients, 17 (73.9%) had P-ANCA and 6 patients (26.1%) had C-ANCA.