ANCA stands for “Anti-Neutrophil Cytoplasmic Antibody.” ANCA antibodies are associated with certain types of small-vessel vasculitis. They can be divided into two primary patterns based on immunofluorescence staining:
- c-ANCA (cytoplasmic pattern) and
- p-ANCA (perinuclear pattern).
Here are some diseases associated with positive ANCA:
- Granulomatosis with Polyangiitis (GPA, formerly known as Wegener’s Granulomatosis):
- Typically associated with c-ANCA and anti-PR3 (proteinase 3) specificity.
- Eosinophilic Granulomatosis with Polyangiitis (EGPA, formerly known as Churg-Strauss Syndrome):
- Some patients with EGPA have p-ANCA with anti-MPO specificity, although many patients with EGPA are ANCA-negative.
- Microscopic Polyangiitis (MPA):
- Typically associated with p-ANCA and anti-MPO (myeloperoxidase) specificity.
- Drug-induced Vasculitis:
- Some medications can induce a vasculitic syndrome with a positive ANCA.
- Common culprits include hydralazine, propylthiouracil, and certain anti-TNF agents.
- Other Conditions:
- Less commonly, ANCA can be positive in other conditions, such as inflammatory bowel disease (IBD), lupus nephritis, and certain types of drug-induced lupus.
- Idiopathic/Primary ANCA-associated Vasculitis:
- Some patients might present with clinical features of vasculitis and positive ANCA without the specific diagnostic criteria for GPA, MPA, or EGPA.
It’s crucial to understand that while ANCA can support the diagnosis of these conditions, it’s not exclusive or definitive. Clinical context, tissue biopsy, and other diagnostic studies are often essential to determine the specific type of vasculitis or related condition. Additionally, a positive ANCA test in the absence of clinical symptoms is not sufficient to diagnose vasculitis. The specificity and pattern of ANCA (anti-PR3 or anti-MPO) can help differentiate between the different ANCA-associated vasculitides.