Emicizumab (MC-Ab) is a humanized bispecific antibody which binds to factors IX-activated and X, speeding up the activation of factor X. It solved some unmet needs in hemophilia A (HA) treatment, such as regimen (once weekly up to once monthly infusion) and route of administration (subcutaneous). Although it is an effective non-replacement alternative in the prophylaxis of people with HA (PwHA) with (PwHAi) or without inhibitor, its safety has not been clarified yet, and a few cases of thrombosis and development of anti-MC-Ab antibody have been described. The aim of this project is to create a national registry to follow up PwHA receiving MC-Ab. EMCase Project is an observational study and any PwHA receiving MC-Ab can be included (e.g., sex, age, inhibitor status etc. are not inclusion nor exclusion criteria). It has been approved centrally by the Committee on Ethics in Research of the Universidade Federal de Minas Gerais (CAAE 10664919.6.0000.5149) and registered in the Brazilian Registry of Clinical Trials (RBR-57rnpz). The treatment will be decided among the patient, the physician, and the interdisciplinary team of the hemophilia treatment center (HTC). The research group developed a brochure with suggestions on classical outcome assessment tools (e.g., bleeding rate, joint health, absenteeism, adherence, quality of life and mortality) which can be evaluated as the judgement of the HTC team. Outcome data, laboratory results and therapeutic progression will be compiled yearly over a maximum of 10 years. Pharmacovigilance and economic analyses will also be included. Finally, a national guidance will be developed. In 2016, there were 10,123 PwHA in Brazil, of whom 4,003 (39.54%) were severe and 451 (4.46%) were PwHAi. There were 268 PwHAi on immune tolerance induction (ITI), of which we can expect a 30% rate of failure. Since MC-Ab has been approved only for PwHAi who failed ITI in Brazil, we expect to include at least 50 PwHAi. Currently, 10 HTCs are registered in the EMCase Project, while 7 other HTCs are in process of formal ethical approval. The first patient was included in July/2020. We expect to establish some outcome assessment tools to aid the interdisciplinary team to manage hemophilia treatment with MC-Ab as well as to help clarifying the safety of this bispecific antibody.