Haemophilia A and B are rare congenital, recessive X-linked disorders caused by lack or deficiency of clotting factor VIII (FVIII) or IX (FIX), respectively. The severity of the disease depends on the reduction of levels of FVIII or FIX, which are determined by the type of the causative mutation in the genes encoding the factors (F8 and F9, respectively). The hallmark clinical characteristic, especially in untreated severe forms, is bleeding (spontaneous or after trauma) into major joints such as ankles, knees and elbows, which can result in the development of arthropathy. Intracranial bleeds and bleeds into internal organs may be life-threatening. The median life expectancy was ~30 years until the 1960s, but improved understanding of the disorder and development of efficacious therapy based on prophylactic replacement of the missing factor has caused a paradigm shift, and today individuals with haemophilia can look forward to a virtually normal life expectancy and quality of life. Nevertheless, the potential development of inhibitory antibodies to infused factor is still a major hurdle to overcome in a substantial proportion of patients. Finally, gene therapy for both types of haemophilia has progressed remarkably and could soon become a reality.

血友病 A 和 B 是罕见的先天性隐性 X 连锁疾病，分别由凝血因子 VIII (FVIII) 或 IX (FIX) 缺乏或缺乏引起。疾病的严重程度取决于 FVIII 或 FIX 水平的降低，这取决于编码因子（F8和F9）的基因中的致病突变类型， 分别）。标志性的临床特征，尤其是未经治疗的严重形式，是踝、膝和肘等主要关节出血（自发性或外伤后），可导致关节病的发展。颅内出血和内脏出血可能会危及生命。直到 1960 年代，平均预期寿命约为 30 年，但基于对缺失因子的预防性替代的有效疗法的改进和发展导致了范式转变，如今血友病患者可以期待几乎正常的生活预期和生活质量。尽管如此，对输注因子的抑制性抗体的潜在发展仍然是很大一部分患者需要克服的主要障碍。最后，