Study to Assess the Tolerability and Safety of Ecallantide in Children and Adolescents With Hereditary Angioedema

Inclusion Criteria: 1. 2 through 15 years of age, inclusive (ie, from the second birthday through the day prior to the sixteenth birthday) at the time of the subject's first attack. 2. Documented diagnosis of HAE type I or II. Diagnosis must be confirmed by a documented immunogenic (below the lower limit of normal) and/or functional (\< 50% of normal levels) C1- Inhibitor deficiency. Diagnosis may be on the basis of historic data or by diagnostic testing conducted at the time of screening. 3. Informed consent (and subject assent as appropriate) signed by the subject's parent(s) or legal guardian(s). Exclusion Criteria: 1. History of an adverse reaction (AE) to Ecallantide in the past 2. Diagnosis of angioedema other than HAE 3. Participation in another clinical study during the 30 days prior to treatment 4. Any known factor/disease that might interfere with the treatment compliance, study conduct, or result interpretation 5. Congenital or acquired cardiac anomalies that interfere significantly with cardiac function. 6. Treatment with angiotensin converting enzyme (ACE) inhibitors within 7 days prior to treatment. 7. Use of hormonal contraception within the 90 days prior to treatment for females of childbearing potential 8. The subject is pregnant or breastfeeding