In other words, if carriers each had two sons 1, total , we would expect there to be about boys with hemophilia. But in that group there would be women who had two sons with hemophilia, women who had one with and one without, and women with no sons with hemophilia. The gene a child will inherit is based purely on chance and can never be truly predicted.
A child's chances of getting a hemophilia gene do not have anything to do with whether or not brothers or sisters have the gene. Each time a woman is pregnant, her chances of having a child with the hemophilia gene are the same Figure It is like rolling dice. The results of one roll do not affect the next roll. A family may have children with the hemophilia gene and children without it. It is also possible for all the children in the family to inherit the normal gene or all to inherit the hemophilia gene.
Figure For a mother who carries the hemophilia gene, the chances of giving birth to a child with hemophilia are the same for each pregnancy. Even though she already has a child with hemophilia, she can still give birth to another. The father's sex chromosomes are labeled XY, with the X chromosome carrying the hemophilia gene. If the baby gets the Y chromosome from the father it will be a boy.
Since the Y chromosome does not carry the hemophilia gene, a son born to a man with hemophilia and a woman who is not a carrier will not have hemophilia. If the baby gets the X chromosome from the father it will be a girl.
The X chromosome from the father with hemophilia will have the hemophilia gene. But the girl also gets an X chromosome from her mother. The normal blood clotting gene on the X chromosome from the mother is dominant, so the baby girl will not have hemophilia.
She will, however, be a hemophilia carrier since she has the hemophilia gene on one of her X chromosomes. So in this case, all sons born to the couple will be normal and all daughters will be hemophilia carriers Figure Father with hemophilia; mother with normal blood clotting gene. Follow the arrows to see the possible gene combinations. The father's sex chromosomes are labeled XY.
The father only passes half of his sex chromosomes to the baby, either the X or the Y. These include mistakes made in DNA replication, such as inadvertently substituting one nucleotide — a DNA building block — for another in the DNA sequence of a gene encoding for a clotting factor.
In very rare cases — approximately one in a million people — an autoimmune disorder can lead to the onset of an acquired form of hemophilia.
The immune system normally produces proteins called antibodies that latch onto viruses, bacteria, and other disease-causing entities that could harm the body, triggering reactions leading to the destruction of those invaders.
In autoimmune diseases, however, the body mistakenly produces antibodies against itself. In the case of acquired hemophilia, the body attacks its own clotting factors, usually factor VIII. This reduces the amount of factor VIII available to effectively promote blood clot formation and prevent major bleeds. Although the specific cause of acquired hemophilia remains unknown, it is sometimes associated with other illnesses usually immune disorders or cancer , allergic reactions to certain medications, or pregnancy.
Hemophilia News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment.
What Are the Signs and Symptoms of Hemophilia? How is Hemophilia Diagnosed? How is Hemophilia Treated? Who is at Risk for Immune Thrombocytopenia? Who is at Risk of Iron-Deficiency Anemia? What are the Symptoms of Iron Deficiency? How is Iron-Deficiency Anemia Diagnosed?
How is Iron-Deficiency Anemia Treated? What Causes Pernicious Anemia? What are the Risk Factors for Pernicious Anemia? What Causes Polycythemia Vera? How is Polycythemia Vera Treated? How is Pulmonary Embolism Treated? What Causes Sickle Cell Disease? Who is at Risk for Sickle Cell Disease? What Causes Hemophilia? Thus, males can have a disease like hemophilia if they inherit an affected X chromosome that has a mutation in either the factor VIII or factor IX gene.
Females can also have hemophilia, but this is much rarer. In such cases both X chromosomes are affected or one is affected and the other is missing or inactive.
In these females, bleeding symptoms may be similar to males with hemophilia. Sometimes a female who is a carrier can have symptoms of hemophilia. In addition, she can pass the affected X chromosome with the clotting factor gene mutation on to her children.
Learn more about the inheritance pattern for hemophilia. Even though hemophilia runs in families, some families have no prior history of family members with hemophilia.
Sometimes, there are carrier females in the family, but no affected boys, just by chance. However, about one-third of the time, the baby with hemophilia is the first one in the family to be affected with a mutation in the gene for the clotting factor.
Hemophilia occurs in about 1 of every 5, male births. Based on recent study that used data collected on patients receiving care in federally funded hemophilia treatment centers during the period , about 20, as many as 33, males in the United States are living with the disorder.
Hemophilia A is about four times as common as hemophilia B, and about half of those affected have the severe form. Hemophilia affects people from all racial and ethnic groups.
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