<qa>  What is the condition that is characterized by congenital lack of functional C1 esteraseHereditary angioedema HAE is a rare disorder characterized by congenital lack of functional C1 esterase inhibitor. If not treated adequately, the acute attacks of HAE can be life-threatening and may even result in fatalities, especially in case of involvement of the larynx.The planned extension study is designed to enrol subjects that participated in the pivotal study in order to provide them with C1-INH for treatment of acute HAE attacks for 24 months or until the licensing procedure for C1-INH is finalized, whatever comes first. 