Eosinophilic granulomatosis with polyangiitis (EGPA; formerly known as Churg-Strauss syndrome) is classified as an anti-neutrophil cytoplasmic antibody (ANCA)-associated small vessel vasculitis. It is a multisystem disorder and can affect every organ system. EGPA is a rare disease, with an estimated prevalence of 1/70,000–100,000 in Europe. As its onset usually occurs in adulthood, data from paediatric patients are limited. We present here a very rare practical EGPA clinical case involving a paediatric patient. Presently, data on mepolizumab usage in paediatric patients are limited, with only a few case reports published.