Severe haemophilia is a rare disease characterized by spontaneous bleedings from early childhood, which may lead to various complications especially in joints. Due to advances in medical care and more specifically in the development of prophylactic strategies by the application of clotting factor concentrates, life expectancy of persons with severe haemophilia has significantly increased over the last decades. This progress requires a long-term follow-up, including into adulthood. The adherence to a regular clinical follow-up and to a prophylactic treatment then depends on how successful patients' transition from childhood to adulthood has been as this process involves a transfer of responsibility from parents to patients concerning the management of their health. Beyond the issue of patients' adherence, a suboptimal transition may also impair quality of life and the entry into adulthood, especially at the social, emotional and professional levels. Only a few studies have been conducted to identify the specific needs and difficulties young persons with severe haemophilia experience during their transition from childhood to adulthood, and none of these studies has been carried out in France where the features of the health care system are very specific.

Therefore, this study aims to address the issue of transition into adulthood among young persons with severe haemophilia in France. This study will focus not only on the facilitators and barriers of the access to health care but also, from a more global perspective, on all the specific concerns and difficulties they may experience as they grow into adulthood which may impair their long-term health related quality of life as well as their personal empowerment. This study will also allow to identify some of the socio- cognitive, emotional, and familial determinants of a good transition into adulthood.

The main objective of this study is to assess the impact of transition from adolescence into adulthood especially on adherence to health care, among young people with severe haemophilia in France.

The operational objectives of this study are: i) to compare the level of adherence in adolescents and in young adults (YA) ii) to identify determinants (medical, organisational, socio-demographic and social, and psychosocial and behavioural factors) of the level of adherence in YPWH (young people with haemophilia), iii) to assess specific factors involved in suboptimal level of adherence in the sub-groups of adolescents on one hand and of YA on the other hand, iv) to identify groups of patients (clusters) regarding both their level of adherence and their psychosocial characteristics, v) to examine trough a qualitative approach YPWH needs and expectations towards the health care system during the transition process, and to identify some ways to improve their global care.

This study is an exploratory, observational, multicentric, transversal study aimed at describing the perceptions of adolescents (14-17 years old) with severe haemophilia to those of young adults (20-29 years old) regarding their expectations and their feelings about growing into adulthood. Every patient enrolled in the FranceCoag national cohort (cohort of French patients suffering from inherited deficiencies of coagulation proteins), suffering from severe haemophilia, aged from 14 to 17 years old or from 20 to 29 years old, will be offered to get enrolled in the TRANSHEMO study (expected number eligible of participants: 154 adolescents and 389 young adults). , among whom 70% are expected to take part in the study). The patients' participation in this study will not modify their medical or paramedical care. A multifocal approach which combines both quantitative and qualitative data collection will be proposed.

Inclusion Criteria:

• Patients with severe haemophilia
• Patients enrolled in the FranceCoag national cohort
• Patients aged from 14 to 17 years old (adolescents group) or from 20 to 29 years old (young adults group)
• Adults patients having given their agreement to participate in the study, or minor patients authorized to participate in the study by their parents or their legal representatives

Exclusion Criteria:

• Patients with comprehension problems
• Patients unable to read or to write
• Adults patients not having given their agreement to participate in the study, or minor patients unauthorized to participate in the study by their parents or their legal representatives

cohort of persons with severe haemophilia