Hemophilia is a recessive genetic disorder, carried by a mutation on the X chromosome. Males receive an X chromosome from their mother and a Y from their father; females receive an X from both parents. This means that if a male has a mutation to his X chromosome that causes hemophilia, he will have hemophilia. If one X chromosome is affected for a woman, the woman’s other X chromosome can take over and produce the necessary clotting factors. Men do not have another X chromosome to fall back on, and have a much higher chance of having hemophilia because of this. In order for a female to be affected by hemophilia, both her X chromosomes have to be affected; because a son receives his only X chromosome from his mother, if his mother is a hemophiliac he will be too. If his mother carries the gene but is unaffected, he has a 50% chance of being affected.
A hemophiliac father’s daughters will carry the gene for hemophilia, but his sons will be unaffected because his sons would receive Y chromosomes from him. As with many genetic disorders, hemophilia can also occur as a spontaneous mutation (as opposed to being passed down through genes). Hemophilia is a spontaneous mutation in about one out of three cases. Right: a short video summarizing the inheritance of hemophilia
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As was seen in The Circulatory System, many clotting factors are involved in the process to repair defects in blood vessels. Hemophilia occurs due to a lack of clotting factors.
The severity of the symptoms can range from being only noticeable during surgeries and dental work, to regular bleeding. This depends on the severity of the disorder. Symptoms revolve around excessive bleeding and include:
Hemophilia is usually diagnosed during infanthood or childhood, especially when an infant acquires bruises from learning to walk; in severely affected individuals, the disorder might be apparent right after birth.
People with 5-40% of the normal amount of clotting factors present in blood are mild hemophiliacs. Those with 1-5% of the normal amount are moderate hemophiliacs, and those with less than 1% have severe hemophilia.
Some female carriers for hemophilia may show mild symptoms of the disorder, but their other X chromosome helps to mask/dilute the symptoms.
The severity of the symptoms can range from being only noticeable during surgeries and dental work, to regular bleeding. This depends on the severity of the disorder. Symptoms revolve around excessive bleeding and include:
- Frequent and/or heavy nosebleeds
- Being easily bruised
- Large, lumpy bruises (as blood continues to come out of broken blood vessels and pools below the skin
- Bleeding for no reason
- Bleeding in joints, which can cause discomfort, pain, limited range of motion, arthiritis and permanent damage to the joint
- Bleeding that does not stop after surgery or dental work (eg getting a tooth removed)
- Blood present in urine or stool
- Heavy menses (called menorrhagia)
- swollen joints
Hemophilia is usually diagnosed during infanthood or childhood, especially when an infant acquires bruises from learning to walk; in severely affected individuals, the disorder might be apparent right after birth.
People with 5-40% of the normal amount of clotting factors present in blood are mild hemophiliacs. Those with 1-5% of the normal amount are moderate hemophiliacs, and those with less than 1% have severe hemophilia.
Some female carriers for hemophilia may show mild symptoms of the disorder, but their other X chromosome helps to mask/dilute the symptoms.
swollen joints are common among those suffering from severe hemophilia; bleeding in the joints is also known as synovitis