This child may be the first in the family to have hemophilia and to carry the defective factor gene.
In some cases, the genetic mutation occurs in the mother, and she finds out she is a carrier after she has a child with hemophilia through DNA testing.
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Publications Dateline Blood Brotherhood Book. Hemophilia B Inheritance Patterns. However, a small percentage of female carriers have less than half the normal amount of coagulation factor and are at higher risk of having abnormal bleeding episodes, particularly after an injury, surgery, or tooth extraction.
Hemophilia C is also primarily inherited , but it does not follow an X-linked pattern because the mutation that causes it affects a gene found on chromosome 4 an autosomal or non-sex chromosome. Hemophilia C, therefore, affects both genders equally. People who carry one faulty copy of the gene causing hemophilia C usually are asymptomatic and do not know they are carriers. If two carriers have a child together, there is a 25 percent chance that the child will inherit one faulty copy of the gene from each parent and develop the disease.
There is also a 50 percent chance that any child will be a carrier like the parents, and a 25 percent chance that the child will not inherit a copy of the disease-causing mutation and neither develop the disease nor be a carrier. Hemophilia News Today is strictly a news and information website about the disease.
It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment.
Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. Envelope icon Subscribe to our newsletter Get regular updates to your inbox. Your Email. It is very rare for a man with hemophilia and a woman who is a carrier to get together.
That is why there have been only a few girls born with hemophilia. Father with hemophilia; mother a carrier. In some families, there is no known family history of hemophilia.
The hemophilia gene seems to appear from nowhere and the family is shocked and confused. There are several reasons this could happen. First, the family may not know about or may have forgotten ancestors with hemophilia. Second, the gene for hemophilia may have been passed down by carrier females without anyone knowing. For several generations, the women may have had no boy children or by chance had only normal boys.
No one would have known about the hemophilia gene. Third, hemophilia may appear in families with no history of it if the normal blood clotting gene suddenly becomes messed up a spontaneous genetic mutation. Normally, genes are exactly copied generation after generation.
Sometimes, though, a gene may become faulty. It may give different or wrong directions to the body. This change in the gene is called a mutation. The effects of the faulty gene may be noticed right away. Or they might not be seen until the gene is passed on to a baby. So the change in the gene may have happened in the parent or in the baby. The change in the gene can be caused by something in the environment. It also seems to happen without any clear cause.
Since they are nature's way of bringing about change, not all gene mutations are harmful. The hemophilia gene can occur in a man or woman this way. The blood clotting gene suddenly becomes faulty. The gene may be passed by female carriers for several generations before hemophilia appears in a boy baby. Probably not. Mutations in blood clotting genes would still happen, making new carriers and new people with hemophilia.
It is believed that as many as one-third of the babies born with hemophilia are caused by new gene mutations. Once the hemophilia gene is present, the chance of passing it on exists. It is possible, however, for hemophilia to disappear from the family tree. This can happen if all family members who have hemophilia or who carry the hemophilia gene give birth to children who by chance do not get the gene. The clotting factor level will be about the same from one generation to the next.
So the daughters of a man with severe hemophilia will all carry the gene for severe. The same goes for men with mild and moderate hemophilia.
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