Hereditary angioedema secondary to C1-inhibitor deficiency is a rare autosomal dominant disorder characterized by a deficiency of C1 esterase inhibitor.An eight-year-old girl showed periorbital painless swelling, diagnosed as ethmoiditis. A craniofacial scan did not evidence a paranasal sinus involvement, C1INH levels were undetectable, with low C4 levels: 7.6 mg/dl and C1INH: <8.46 mg/dl. The genetic study identified a rare mutation of the C1INH gene. This clinical report is of relieve because paediatric cases described in literature are rare, did not presented a positive family history, and received a diagnosis after many attacks. Furthermore our girl received a prompt diagnosis of HAE at the first attack of angioedema.