Study to Evaluate Ecallantide in Paediatric Patients With Acute Attacks of Hereditary Angioedema

Inclusion Criteria: 1. Male or female from 2 years of age and prepubertal 2. Physician diagnosis and history of HAE (Type I or II) including laboratory results showing C1-1NH activity below the lower limit of normal or up to 15% above the lower limit of the normal range 3. Present at the site with moderate to severe signs and symptoms of an acute attack of HAE within 8 hours of recognition of the onset of the attack. Spontaneous resolution of the attack must not have begun before the administration of study drug. 4. Must have signed informed consent by parent or caregiver. Exclusion Criteria: 1. \<2 years of age or have reached puberty 2. Received treatment with ecallantide within previous 72 hours 3. Received an investigational drug or device, other than ecallantide, within 30 days prior to the screening visit 4. Pharyngeal/laryngeal symptoms 5. Mild attacks including mild edema of the extremities and mild abdominal attacks 6. Are unable or unwilling to give informed consent (parent or caregiver) 7. Any other condition that, in the opinion of the investigator, may compromise the safety or compliance of the patient or would preclude the patient from successful completion of the study