Females who are carriers usually have enough clotting factors from their one normal gene to prevent serious bleeding problems, though some may present as mild haemophiliacs. Complications
Severe complications are much more common in cases of severe and moderate haemophilia. Complications may arise from the disease itself or from its treatment:
Deep internal bleeding, e.g. deep-muscle bleeding, leading to swelling, numbness or pain of a limb. Joint damage from haemarthrosis (haemophilic arthropathy), potentially with severe pain, disfigurement, and even destruction of the joint and development of debilitating arthritis. Transfusion transmitted infection from blood transfusions that are given as treatment. Adverse reactions to clotting factor treatment, including the development of an immune inhibitor which renders factor replacement less effective. Intracranial haemorrhage is a serious medical emergency caused by the buildup of pressure inside the skull. It can cause disorientation, nausea, loss of consciousness, brain damage, and death.Haemophilic arthropathy is characterized by chronic proliferative synovitis and cartilage destruction. If an intra-articular bleed is not drained early, it may cause apoptosis of chondrocytes and affect the synthesis of proteoglycans. The hypertrophied and fragile synovial lining while attempting to eliminate excessive blood may be more likely to easily rebleed, leading to a vicious cycle of hemarthrosis-synovitis-hemarthrosis. In addition, iron deposition in the synovium may induce an inflammatory response activating the immune system and stimulating angiogenesis, resulting in  cartilage and bone destruction. Genetics
Typically, females possess two X-chromosomes, and males have one X and one Y-chromosome.
Research
Gene therapy
In those with severe haemophilia, gene therapy may reduce symptoms to those that a person with mild or moderate haemophilia might have. The best results have been found in haemophilia B. In 2016 early stage human research was ongoing with a few sites recruiting participants. In 2017 a gene therapy trial on nine people with haemophilia A reported that high doses did better than low doses. It is not currently an accepted treatment for haemophilia.In July 2022 results of a gene therapy candidate for haemophilia B called  FLT180 were announced, it works using an adeno-associated virus (AAV) to restore the clotting factor IX (FIX) protein, normal levels of the protein were observed with low doses of the therapy but immunosuppression was necessitated to decrease the risk of vector-related immune responses. See also
Coagulopathy
Purpura secondary to clotting disorders
Von Willebrand disease
World Federation of Hemophilia

References
External links

Haemophilia at Curlie
World Federation of Hemophilia