The overall objective is to enroll patients with acquired hemophilia A (AHA) who are prescribed and treated with Obizur, to assess safety, and to describe factors related to safety, utilization and effectiveness in a real-world setting.

This study is a multi-center, uncontrolled, open-label, non-interventional post-marketing safety surveillance study to describe the use of Obizur in patients with acquired hemophilia A (AHA), and secondarily, where data are available, to describe the hemostatic effectiveness and immunogenicity of Obizur.

Patients should be enrolled at the earliest possible time point after initiating Obizur.

In an attempt to collect safety and utilization data on patients treated with Obizur since Food and Drug Administration (FDA) approval in October 2014, Baxalta will make an effort to identify all persons treated with Obizur and to collect data for as many patients as possible.

Inclusion Criteria:

1. Participant is ≥18 years of age at the time of informed consent.
2. Participant has AHA, and is being treated/was treated with Obizur.
3. Participant or the participant's legally authorized representative is willing and able to provide informed consent, unless informed consent is not required

Exclusion Criteria:

1. Participant has a known anaphylactic reaction to the active substance, to any of the excipients, or to hamster protein.
2. Participant has a concomitant bleeding disorder(s) other than acquired hemophilia A (AHA).
3. Participant has participated in another clinical study involving a medicinal product or device within 30 days prior to enrollment or is scheduled to participate in another clinical study involving a medicinal product or device during the course of the study.

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.