CLINICAL SIGNIFICANE:
Cytoplasmic anti-neutrophil cytoplasmic antibodies are diffuse and granular on cytoplasmic staining pattern observed by indirect immunofluorescence (IIF) microscopy when serum antibodies bind to indicator neutrophils. Proteinase 3 (PR3) present in azurophilic granules of neutrophils is the major antigen for c-ANCA. Diffuse fine granular cytoplasmic fluroesence (cANCA) is typically found in Wegener‘s granulomatosis, in some cases of microscopic polyarteritis and Churg Strauss syndrome , and in some cases of crescentic and segmental necrotising glomerulonephritis, but is rare in other conditions. The target antigen is usually proteinase. Protinase 3 have been identified as the principal antigens for cANCA . The enzymes are localized in the primary granules of neutrophils.
FREQUENCY IN VASCULITIS
CLINICAL APPLICATIONS:
C-ANCA
- C-ANCA are present in – 90% of patients with active Generalized Wegener ‘s Granulomatosis (WG) . Sensitivity decreases to 60-70% with inactive or limited WG. A negative C-ANCA, therefore, doesn’t exclude a diagnosis of WG. Because changing titers often parallel disease activity.
- C-ANCA are frequently seen in microscopic polyarteritis nodosa and idiopathic necrotizing and crescentic glomerulonephritis (without immune deposits ), which are possibly related to WG.
- Although the majority of WG patients have C-ANCA and most patients with ANCA-associated glomerulonephritis without systemic manifestations have P-ANCA, there is some overlap.