| • | detected using an immunofluorescence technique; positive test results reveal one of two basic patterns of staining (cytoplasmic or perinuclear): |
c-anca
| • | = antibodies directed against proteinase 3 |
| • | sensitive (96%) and specific for the presence of active Wegener’s granulomatosis (though it can also be seen in PAN and Churg-Strauss) |
| • | titer tends to correlate with disease activity (within a given patient) |
p-anca
| • | antibodies that cause a p-ANCA pattern are directed against several proteins, most commonly myeloperoxidase or elastase |
| • | has been termed “artefactual” because it appears only after cells have been fixed with alcohol |
| • | present in 25-70% of cases of Churg-Strauss (strongest association) |
| • | occasionally present in WG, but can be found in other vasculitides, glomerulonephritis, and IBD |
| • | PAN may show p-ANCA positive but it is non-specific and not very helpful diagnostically |
| • | Wegener’s granulomatosis (c-ANCA – 96% sensitive) |
| • | Churg-Strauss syndrome (p-ANCA – 25-70%) |
| • | microscopic polyangiitis |
clinically they can be separated by specific features:
| • | Wegener’s – necrotizing granulomatous inflammation in the upper or lower respiratory tract, the kidneys, and occasionally the skin |
| • | Churg-Strauss – asthma and eosinophilia |
| • | the absence of specific features leads to the diagnosis of microscopic polyangiitis |
Medium Vessel Vasculitis:
| • | renal failure occurs much less frequently in CSS compared with others |
| • | typically lungs not involved in PAN |
| • | CSS shows significant overlap with WG and PAN |
|
ANCA
|
Skin:
|
Systemic:
|
PAN
|
+/- pANCA (not helpful)
|
(50%) cutaneous and subcutaneous nodules +/- ulceration, livedo, esp. LE’s
|
| • | 60% mononeuritis multiplex; |
|
Wegener’s
|
cANCA sensitive (96%); follow titers
|
(66%) cutaneous and subcutaneous nodules +/- ulceration, palpable purpura
|
| • | lung - upper and lower respiratory tract |
(necrotizing granulomatous inflammation)
|
Churg-Strauss
|
pANCA (25-70%); follow titers
|
tender nodules on scalp and extremities
|
| • | kidneys spared (usually) |
| • | lungs - late onset asthma |
|
|
|
