HAE is a rare condition. It causes sudden swelling under the skin and inside the body, like in the belly, throat, or genitals. This swelling happens because of a temporary leak in blood vessels but does not cause itching or hives. HAE is classified based on the amount of a protein in the blood called C1 inhibitor (C1-INH): HAE with normal C1-INH levels and HAE with limited or insufficient C1-INH levels (C1-INH deficiency). This study will concentrate on children with HAE C1-INH deficiency who have received Takhzyro (Lanadelumab) as prophylactic treatment.

The main goal of the study is to assess how well lanadelumab works in children with HAE-C1INH deficiency in everyday life. This will be measured by checking how long children who receive lanadelumab will be free of HAE attacks.

Other goals are to understand how children with HAE-C1INH deficiency are being treated with lanadelumab, how well the treatment works for them, how safe it is and how often these children need to use healthcare services (like doctor visits, hospital stays, etc.) because of their condition.

The study will only look at data already existing in the participants' medical records. No treatment will be given as part of the study.

Inclusion Criteria:

1. Participant is aged 2 to less than (<) 12 years at the time of lanadelumab initiation and is expected to have at least 6 months of follow-up information before turning 12.
2. Participant has physician-confirmed diagnosis of HAE-C1INH.
3. Participant initiated LTP with lanadelumab during the eligibility period.
4. Signed consent/assent (where required by local regulations).
5. Participant's medical record contains documentation of HAE attacks in the pre-index period and after lanadelumab initiation.

Exclusion Criteria:

1. Participant was enrolled in a therapeutic investigational drug (lanadelumab or other drug) or device trial at index date.
2. Participant with no documented HAE attacks in the 12 months prior to index date.

Paediatric participants who have been diagnosed with HAE-C1INH in Germany, France, United Kingdom (UK), Israel, Argentina and Serbia.

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.