Open-Label C1 Esterase Inhibitor (C1INH-nf) for the Prevention of Acute Hereditary Angioedema (HAE) Attacks

Inclusion Criteria: \- History of at least 1 HAE attack per month or any history of laryngeal edema In addition, this study was open to all subjects who: * Completed participation in LEVP2005-1/B (NCT01005888) any time after the final prophylactic therapy in Part B * Were enrolled but not randomized in LEVP2005-1/A (NCT00289211) after Part A was closed * Were enrolled and randomized in LEVP2005-1/A after LEVP2005-1/B was closed to enrollment, any time after the 3-day telephone follow-up * Were excluded from LEVP2005-1 for any of the following reasons: * Pregnancy or lactation * Age less than 6 years * Narcotic addiction * Presence of anti-C1 inhibitor (C1INH) autoantibodies * Were not enrolled in LEVP2005-1 after enrollment in LEVP2005-1 was closed, under the following circumstances: * Had a diagnosis of HAE: evidence of a low C4 level plus either a low C1INH antigenic level or a low C1INH functional level, or * Had a known HAE-causing C1INH mutation, or * Had a diagnosis of HAE based on a strong family history of HAE as determined by the principal investigator Exclusion Criteria: * History of allergic reaction to C1INH or other blood products * Participated in any other investigational drug study within the past 30 days other than those sponsored by Lev Pharmaceuticals * Received blood or a blood product in the past 60 days other than C1INH-nf