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According to the Centers for Disease Control and Prevention (CDC):
According to the US Centers for Disease Control and Prevention (CDC), hemophilia occurs in approximately 1 in 5,617 live male births. There are between 30,000 – 33,000 males with hemophilia in the US*. More than half of people diagnosed with hemophilia A have the severe form. Hemophilia A is four times as common as hemophilia B. Hemophilia affects all races and ethnic groups.
The Genetics of HemophiliaA 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. How is Hemophilia Inherited? Hemophilia is passed down from parents to children. Is Hemophilia Sex linked? Yes, hemophilia is a sex linked disorder. The X and Y sex chromosomes help determine hemophilia inheritance patterns. The gene for hemophilia is carried on the X chromosome. Is Hemophilia Dominant or Recessive? Hemophilia is inherited in an X-linked recessive manner. Females inherit two X chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome from their mother and a Y chromosome from their father (XY). That means if a son inherits an X chromosome carrying hemophilia from his mother, he will have hemophilia. It also means that fathers cannot pass hemophilia on to their sons. But 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. A daughter who inherits an X chromosome that contains the gene for hemophilia is called a carrier. She can pass the gene on to her children. Many women who carry the hemophilia gene also have low factor expression, which can result in heavy menstrual bleeding, easy bruising, and joint bleeds. Some women who have the hemophilia gene have factor expression low enough to be diagnosed with hemophilia. For a female carrier, there are four possible outcomes for each pregnancy: 1. A girl who is not a carrier 2. A girl who is a carrier 3. A boy without hemophilia 4. A boy with hemophilia Severity
• Severe (factor levels less than 1%) represent approximately 60% of cases • Moderate (factor levels of 1-5%) represent approximately 15% of cases • Mild (factor levels of 6%-30%) represent approximately 25% of cases What are the Symptoms of Hemophilia A?
Normal levels of FVIII range from 50% to 150%. Levels below 50% – or half of what is needed to form a clot – determine a person’s symptoms. • Mild hemophilia A: 6% up to 49% of FVIII in the blood. People with mild hemophilia A generally experience bleeding typically only after serious injury, trauma, or surgery. In many cases, mild hemophilia is not diagnosed until an injury, surgery or tooth extraction results in prolonged bleeding. The first episode may not occur until adulthood. Women with mild hemophilia often experience heavy menstrual bleeding, and can hemorrhage (bleed extensively) after childbirth. • Moderate hemophilia A: 1% up to 5% of FVIII in the blood. People with moderate hemophilia A tend to have bleeding episodes after injuries. • Severe hemophilia A. <1% of FVIII in the blood. 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. Many males with severe hemophilia are diagnosed due to bleeding after circumcision. Diagnosis of Hemophilia A
Because of our understanding of hemophilia genetics, most people who have a family history of hemophilia will ask that their baby boys be tested soon after birth to see if they have hemophilia. If there is no family history of hemophilia, people often notice bleeding that takes longer to stop or lots of bruising. Many babies born with severe hemophilia are diagnosed if there is prolonged bleeding after circumcision. For girls, it often takes seeing worsening of symptoms for the diagnosis process to begin. Most girls are not tested for hemophilia before puberty. Heavy periods are a symptom of a bleeding disorder in women and girls. If there is a known family history, it is important to monitor for symptoms. It is recommended that women who have a family history of hemophilia get tested before getting pregnant, to help prevent complications during childbirth. The best place for patients with hemophilia to be diagnosed and treated is at one of the federally funded hemophilia treatment centers (HTCs) that are spread throughout the country. HTCs provide comprehensive care from skilled hematologists and other professional staff, including nurses, physical therapists, social workers and sometimes dentists, dieticians and other healthcare providers, including specialized labs for more accurate lab testing.
How is Hemophilia A Treated?Most treatments for hemophilia A focus on replacing the missing protein, FVIII (8), so a person can form a clot, and so reduce or eliminate the bleeds associated with the disorder. Treatments that work to prevent bleeding through new mechanisms have recently come to the market or are in clinical trials. People with hemophilia A have several different medication options for treatment. Learn about treatment options for hemophilia. Living with Hemophilia A
Explore NHF's Steps for Living to learn more about living with hemophilia A. *"Occurrence rates of haemophilia among males in the United States based on surveillance conducted in specialized haemophilia treatment centres," Soucie et al  Many people who have or have had family members with hemophilia will ask that their baby boys get tested soon after birth. About one-third of babies who are diagnosed with hemophilia have no other family members with the disorder. A doctor might check for hemophilia if a newborn is showing certain signs of hemophilia. Diagnosis includes screening tests and clotting factor tests. Screening tests are blood tests that show if the blood is clotting properly. Clotting factor tests, also called factor assays, are required to diagnose a bleeding disorder. This blood test shows the type of hemophilia and the severity. Families With a History of HemophiliaAny family history of bleeding, such as following surgery or injury, or unexplained deaths among brothers, sisters, or other male relatives such as maternal uncles, grandfathers, or cousins should be discussed with a doctor to see if hemophilia was a cause. A doctor often will get a thorough family history to find out if a bleeding disorder exists in the family. Many people who have or have had family members with hemophilia will ask that their baby boys get tested soon after birth. In the best of cases, testing for hemophilia is planned before the baby’s delivery so that a sample of blood can be drawn from the umbilical cord (which connects the mother and baby before birth) immediately after birth and tested to determine the level of the clotting factors. Umbilical cord blood testing is better at finding low levels of factor VIII (8) than it is at finding low levels of factor IX (9). This is because factor IX (9) levels take more time to develop and are not at a normal level until a baby is at least 6 months of age. Therefore, a mildly low level of factor IX (9) at birth does not necessarily mean that the baby has hemophilia B. A repeat test when the baby is older might be needed in some cases. Learn more about the inheritance pattern for hemophilia. Families With No Previous History of HemophiliaAbout one-third of babies who are diagnosed with hemophilia have no other family members with the disorder. A doctor might check for hemophilia in a newborn if:
Those with severe hemophilia can have serious bleeding problems right away. Thus, they often are diagnosed during the first year of life. People with milder forms of hemophilia might not be diagnosed until later in life. Screening TestsScreening tests are blood tests that show if the blood is clotting properly. Types of screening tests: Complete Blood Count (CBC)This common test measures the amount of hemoglobin (the red pigment inside red blood cells that carries oxygen), the size and number of red blood cells and numbers of different types of white blood cells and platelets found in blood. The CBC is normal in people with hemophilia. However, if a person with hemophilia has unusually heavy bleeding or bleeds for a long time, the hemoglobin and the red blood cell count can be low. Activated Partial Thromboplastin Time (APTT) TestThis test measures how long it takes for blood to clot. It measures the clotting ability of factors VIII (8), IX (9), XI (11), and XII (12). If any of these clotting factors are too low, it takes longer than normal for the blood to clot. The results of this test will show a longer clotting time among people with hemophilia A or B. Prothrombin Time (PT) TestThis test also measures the time it takes for blood to clot. It measures primarily the clotting ability of factors I (1), II (2), V (5), VII (7), and X (10). If any of these factors are too low, it takes longer than normal for the blood to clot. The results of this test will be normal among most people with hemophilia A and B. Fibrinogen TestThis test also helps doctors assess a patient’s ability to form a blood clot. This test is ordered either along with other blood clotting tests or when a patient has an abnormal PTexternal icon or APTT testexternal icon result, or both. Fibrinogen is another name for clotting factor I (1). Clotting Factor TestsClotting factor tests, also called factor assays, are required to diagnose a bleeding disorder. This blood test shows the type of hemophilia and the severity. It is important to know the type and severity in order to create the best treatment plan.
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