Clinical aspects of non-severe hemophilia Focus on bleeding, joint and treatment outcomes

Hemophilia A and B are rare inherited bleeding disorders, caused by mutations in the F8 or F9 gene on the X-chromosome leading to a deficiency of coagulation factor VIII (FVIII) or coagulation factor IX (FIX), respectively. As a result, persons with decreased coagulation FVIII/IX levels have an increased bleeding tendency. Classification of disease severity is based on the endogenous FVIII/IX level, ranging from severe (FVIII/IX <1%) to non-severe (moderate; FVIII/IX 1-5% and mild; FVIII/IX 5-40%). Hemophilia is characterized by the occurrence of muscle and joint bleeds, in which joint bleeds may lead to irreversible joint damage. Even though it is commonly known that persons with non-severe hemophilia have a milder bleeding phenotype in comparison to persons with severe hemophilia, detailed information on the clinical phenotype and interindividual variation in persons with non-severe hemophilia is lacking. This thesis focuses on persons with non-severe hemophilia A and B and aims to gain more insights into the clinical phenotype (bleeding and joint outcomes), diagnostical aspects and treatment in this population. The findings of this research increase our knowledge on what may be expected in persons with non-severe hemophilia and may allow for the optimization of treatment and management of this population.