Introduction
Anti-neutrophil cytoplasmic antibodies (ANCA) are important as they are associated with a number of small-vessel vasculitides, including:
Clinical features
ANCA associated vasculitis is more common with increasing age. Whilst each condition has its own distinct features, there are a number of common findings:
- renal impairment
- caused by immune complex glomerulonephritis → raised creatinine, haematuria and proteinuria
- respiratory symptoms
- dyspnoea
- haemoptysiis
- systemic symptoms
- fatigue
- weight loss
- fever
- vasculitic rash: present only in a minority of patients
- ear, nose and throat symptoms
- sinusitis
Investigations
General approach to first-line investigations:
There are two main types of ANCA - cytoplasmic (cANCA) and perinuclear (pANCA). There is considerable overlap between which antibodies are found in which condition, but as a rule of thumb:
- urinalysis for haematuria and proteinuria
- bloods:
- urea and creatinine for renal impairment
- full blood count: normocytic anaemia and thrombocytosis may be seen
- CRP: raised
- ANCA testing (see below)
- chest x-ray: nodular, fibrotic or infiltrative lesions may be seen
ANCA types
There are two main types of ANCA - cytoplasmic (cANCA) and perinuclear (pANCA). There is considerable overlap between which antibodies are found in which condition, but as a rule of thumb:
- cANCA - granulomatosis with polyangiitis
- pANCA - eosinophilic granulomatosis with polyangiitis + others (see below)
| cANCA | pANCA | |
|---|---|---|
| Target | Serine proteinase 3 (PR3) | myeloperoxidase (MPO) |
| Granulomatosis with polyangiitis | 90% | 25% |
| Eosinophilic granulomatosis with polyangiitis | Low | 50% |
| Microscopic polyangiitis | 40% | 75% |
| Other associated conditions | Ulcerative colitis (70%) Primary sclerosing cholangitis (70%) Anti-GBM disease (25%) Crohn's disease (20%) | |
| Use for monitoring | Some correlation between cANCA levels and disease activity | Cannot use level of pANCA to monitor disease activity |
Management
Once suspected, ANCA associated vasculitis should be managed by specialist teams (e.g. renal, rheumatology, respiratory) to allow an exact diagnosis to be made. Kidney or lung biopsies may be taken to aid the diagnosis.
The mainstay of management is immunosuppressive therapy.
The mainstay of management is immunosuppressive therapy.
TYPES
Eosinophilic granulomatosis with polyangiitisGranulomatosis with polyangiitis
Microscopic polyangiitis