People with severe hemophilia A experience bleeding following an injury and may have frequent spontaneous bleeding episodes – bleeds that occur without obvious cause – often into their joints and muscles. People with moderate hemophilia A tend to have bleeding episodes after injuries. Moderate hemophilia A: 1% up to 5% of FVIII in the blood.Women with mild hemophilia often experience heavy menstrual bleeding, and can hemorrhage (bleed extensively) after childbirth. The first episode may not occur until adulthood. In many cases, mild hemophilia is not diagnosed until an injury, surgery or tooth extraction results in prolonged bleeding. People with mild hemophilia A generally experience bleeding typically only after serious injury, trauma, or surgery. Mild hemophilia A: 6% up to 49% of FVIII in the blood.Levels below 50% – or half of what is needed to form a clot – determine a person’s symptoms.
Normal levels of FVIII range from 50% to 150%. How often a person bleeds and the severity of those bleeds depends on how much FVIII a person produces naturally. Bleeds can occur internally, into joints and muscles, or externally, from minor cuts, dental procedures, or injuries. People with hemophilia A bleed longer than other people.
Mild (factor levels of 6%-30%) represent approximately 25% of cases. Moderate (factor levels of 1-5%) represent approximately 15% of cases. Severe (factor levels less than 1%) represent approximately 60% of cases. (percentage breakdown of overall hemophilia population by severity) Some women who have the hemophilia gene have factor expression low enough to be diagnosed with hemophilia.įor a female carrier, there are four possible outcomes for each pregnancy: Many women who carry the hemophilia gene also have low factor expression, which can result in heavy menstrual bleeding, easy bruising, and joint bleeds. She can pass the gene on to her children. A daughter who inherits an X chromosome that contains the gene for hemophilia is called a carrier. It also means that fathers cannot pass hemophilia on to their sons.īut because daughters have two X chromosomes, even if they inherit the hemophilia gene from their mother, most likely they will inherit a healthy X chromosome from their father and not have hemophilia. That means if a son inherits an X chromosome carrying hemophilia from his mother, he will have hemophilia. Males inherit an X chromosome from their mother and a Y chromosome from their father (XY). Females inherit two X chromosomes, one from their mother and one from their father (XX). Hemophilia is inherited in an X-linked recessive manner. The gene for hemophilia is carried on the X chromosome. The X and Y sex chromosomes help determine hemophilia inheritance patterns. Yes, hemophilia is a sex linked disorder. Hemophilia is passed down from parents to children. Learn more about how blood clots at NHF’s Steps for Living.Ī baseline understanding of hemophilia genetics is important for those individuals who have reason to suspect that a genetic predisposition for hemophilia exists in their family. Hemophilia affects all races and ethnic groups. Hemophilia A is four times as common as hemophilia B. More than half of people diagnosed with hemophilia A have the severe form. There are between 30,000 – 33,000 males with hemophilia in the US*. Although it is passed down from parents to children, about 1/3 of cases found have no previous family history.Īccording to the US Centers for Disease Control and Prevention (CDC), hemophilia occurs in approximately 1 in 5,617 live male births. Hemophilia A, also called factor VIII (8) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII (FVIII), a clotting protein.
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