Anti-acetylcholine receptor (AChR) antibodies

Vasculitides comprise a heterogeneous group of disorders characterised by inflammation and necrosis of the walls of arteries and veins of different calibres supplying various body districts. Symptoms include signs of local and systemic inflammation and secondary symptoms arising from reduced tissue perfusion.

The term “ANCA-associated systemic vasculitides” (AAV), recognised by the Chapel Hill Consensus Conference, identifies primary vasculitides with similar clinical and pathological features in which antibodies to neutrophil cytoplasmic constituents are frequently detected.

AAVs are classified into three main forms, based on clinical phenotype and ANCA subtype:

• Granulomatosis with polyangiitis (GPA, formerly Wegener’s granulomatosis)
• Microscopic polyangiitis (MPA)
• Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg–Strauss syndrome)

There are different methods for ANCA detection. Indirect immunofluorescence (IIFT) on neutrophil granulocytes allows identification of the main associated fluorescence patterns:

• cytoplasmic pattern (cANCA), mainly associated with anti-proteinase 3 (PR3) antibodies in patients with GPA
• perinuclear pattern (pANCA), mainly associated with myeloperoxidase (MPO) antibodies in patients with MPA and EGPA
• atypical patterns (X-ANCA), associated with antibodies other than PR3 and MPO, found in non-vasculitic diseases such as chronic inflammatory bowel diseases, primary sclerosing cholangitis, autoimmune liver diseases, connective tissue diseases, rheumatoid arthritis, malignant tumours and infections.