Eosinophilic granulomatosis with polyangiitis is a small-to-medium vessel vasculitis characterised by asthma, eosinophilia, and systemic vasculitis affecting multiple organs, particularly the lungs and kidneys. It is clinically significant due to its potential to cause severe organ damage and requires prompt diagnosis and treatment to prevent complications such as renal failure or pulmonary haemorrhage. A key association is its link to anti-neutrophil cytoplasmic antibodies (ANCA), particularly perinuclear ANCA.