BACKGROUND: Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent angioedema episodes caused by a quantitative or functional defect of the plasma protein C1 esterase inhibitor (C1-INH). Relapsing skin swellings, abdominal pain attacks and upper airway obstruction constitute the typical clinical manifestations. The incidence and severity of angioedema attacks are highly variable among HAE patients.CASES: We report on 4 patients with HAE type I, members of the same family, originating from a Greek island. The patients, 2 males and 2 females (aged 8-45 years) suffer from recurrent edema episodes (1-2 attacks/month). Skin swellings at the extremities and the face, abdominal episodes and laryngeal edema are the classical clinical triad, with significant variation in the severity and frequency of symptoms among our patients. The new missense mutation in exon 2 of the C1-INH gene, c.1A>G; p.Met-22Val (p.Met1Val), in a heterozygous form was detected in all our patients. Acute and severe attacks are successfully treated with administration of C1-INH concentrate.CONCLUSION: Variability of phenotypic expression of HAE was observed among the affected family members, despite carrying identical mutation of the C1-INH gene. Acute exacerbations of the disease are safely and effectively treated with C1-INH concentrate.