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Living with Classical Homocystinuria

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Living with Classical Homocystinuria Living with Classical Homocystinuria This brochure will help you understand what classical homocystinuria is, how it affects your body, and how you can manage your condition A few words about this brochure What is homocystinuria? Has your doctor diagnosed you or your child You may have heard the word “homocystinuria” with homocystinuria (HO-mo-SIS-tin-YUR- for the first time when your doctor talked to ee-uh)? There are three types of genetic you about possibly having this condition. disorders that cause homocystinuria. Each Homocystinuria is a rare disorder involving type has a different cause and different the amino acid homocysteine (HO-mo-SIS- health issues. This brochure will talk about teen). Amino acids are building blocks that your classical homocystinuria. The information body uses to make proteins. Homocystinuria will help you understand classical occurs when there is a buildup of the amino acid homocystinuria and how you can manage homocysteine in your blood and urine. your condition. High levels of homocysteine can be harmful to your body. You may be reading this brochure because you have classical homocystinuria or Why is there homocysteine because your child or a sibling or a friend in your body? has it. Or perhaps you’re a healthcare professional. Please note the brochure It starts with the foods you eat. Your body addresses “you,” but it’s understood that makes homocysteine from another amino acid “you,” the reader, may not have classical called methionine (meh-THIGH-uh-neen). Most homocystinuria yourself. foods contain some methionine. But high-protein foods such as meat, fish, eggs, or cheese tend to have the most methionine. Plant-based foods such as beans, tofu, and nuts also have higher amounts of methionine. So when you eat these types of foods, more methionine enters your body. Then your body breaks down or metabolizes the methionine you’ve eaten into homocysteine. 2 3 Jason Danielle What causes classical Why do you have Unaffected Unaffected homocystinuria? classical homocystinuria? “carrier” “carrier” R r R r You have classical homocystinuria Classical homocystinuria is a genetic R R R r R r r r if you have an abnormal variation of the condition, which is another way of saying CBS (cystathionine beta-synthase) gene. you inherited it from your parents. Classical The job of the CBS gene is to make CBS homocystinuria occurs when you inherit enzyme. This enzyme helps your body two copies of an abnormal variation of break down homocysteine into cysteine, the CBS gene, one from each parent. (The another amino acid that your body needs. medical term for this kind of inheritance If you have classical homocystinuria, your is autosomal recessive.) Since classical CBS gene makes too little CBS enzyme or homocystinuria is caused by genetics, it is none at all, or it makes CBS enzyme that a lifelong condition. Kayla Brady Jennifer James does not work properly. Without enough Unaffected Unaffected “carrier” Affected 1 in 4 chance 2 in 4 chance 1 in 4 chance CBS enzyme activity, your body cannot break down enough homocysteine to keep If you have classical homocysteine levels within the normal range. homocystinuria, you were born So homocysteine levels build up in your body, This diagram shows with it, even if you didn’t have how classical Both of them could potentially pass which can cause serious health problems. homocystinuria may affect families. In this the abnormal variation of the CBS gene symptoms right away. family, the parents, Jason and Danielle, are to their future children. Kayla has two carriers of classical homocystinuria. Each child normal copies of the CBS gene. She will Other names for classical in the family has a 1 in 4 chance of having pass on a normal copy of the CBS gene homocystinuria are CBS If you have classical homocystinuria and classical homocystinuria. In this case, James, to any future children that she has. your parents do not, then they are carriers their son, has the condition because he inherited deficiency and homocystinuria Being a carrier of classical of the condition. This means they have one two abnormal variations of the CBS gene. The homocystinuria is much more common caused by CBS deficiency. normal copy and one abnormal variation other children – Jennifer, Brady, and Kayla – do than having the condition. That’s why of the CBS gene. They don’t have classical not have classical homocystinuria. But Jennifer many people who are diagnosed with homocystinuria because their normal copy and Brady are carriers of the condition because classical homocystinuria have no known of the CBS gene produces enough of the they have one normal copy and one abnormal family history of the condition. CBS enzyme to keep homocysteine levels variation of the CBS gene. at normal levels. 4 5 How is classical homocystinuria diagnosed? Are there different types of classical homocystinuria? Your doctor will order blood tests screening is not perfect and may not catch Yes – your classical homocystinuria can be: If your body is making enough CBS to determine if you have classical all newborns with the condition. In some • Vitamin B6-responsive or pyridoxine enzyme, then vitamin B6 – also called homocystinuria. If the results show high newborns, the level of methionine may not (PEER-uh-DOX-een)-responsive pyridoxine – may help the CBS enzyme levels of homocysteine and methionine be high enough at the time of the screening do its job. If your body is not making in your blood, then most likely you have test to trigger a positive result. Also, some • Partially vitamin B6-responsive enough CBS enzyme, then vitamin B6 classical homocystinuria. Your doctor may babies who are born early (premature) may or partially pyridoxine-responsive probably won’t help. also suggest more blood testing to identify not be developed enough for the screening • Vitamin B6-non-responsive It is important for your doctor to know the variation in your CBS gene. This is known to be accurate. or pyridoxine-non-responsive what type of classical homocystinuria as “DNA sequencing,” and it’s done by a Some people are not diagnosed with Your doctor will need to do another test you have in order to develop the right special lab. Genetic testing can confirm homocystinuria until after symptoms appear. to determine which type of classical treatment plan for you. a diagnosis of classical homocystinuria. Symptoms may develop at different times homocystinuria you have. This test is called The results from your CBS gene In the United States, every state screens for different people, so diagnosis can occur a vitamin B6 challenge or a pyridoxine testing may suggest whether you will newborns for classical homocystinuria. at any age. And because homocystinuria is challenge. The purpose is to find out how you be vitamin B-6-responsive, but the The screening test measures blood levels rare, some doctors may not recognize the will respond to vitamin B6. only way to know for sure is to do the of methionine. If the newborn screening test symptoms right away and the diagnosis can vitamin B6 challenge test. result is positive, then your doctor will order be delayed. more testing to confirm the result. Newborn “Until I was diagnosed with homocystinuria at age 54, the doctors thought I had Marfan syndrome. When I was around 2 years old, “Samantha had an abnormal newborn screening, I developed dislocated lenses so I had to start wearing really thick and a month or two later a genetic test confirmed her glasses. In high school, I developed scoliosis so I had to wear a back homocystinuria diagnosis. She started treatment right brace 23 hours a day for over a year. I wasn’t allowed to participate away. She’s 2 now, and she’s doing really well. in PE because of my back. Years later I started having trouble She hasn’t had any symptoms.” with blood clots, and at age 46 I had a stroke.” Amber G., mother of Samantha, – Pam P., person living with classical homocystinuria who has classical homocystinuria 6 7 Here’s how the B6 challenge test may be done: How can classical homocystinuria affect your health? 1. While on your normal diet, your blood 4. Two days after being on the higher dose, High homocysteine levels can be harmful to your Bones: homocysteine and methionine levels will your blood homocysteine and methionine body, mainly in four areas: brain, eyes, bones, and • Bones that grow longer than normal, be measured. After your blood sample levels will be measured again. blood. Complications in each of these areas may for example, tall body with long has been drawn, you will take a specific include: 5. If no change has occurred, then you will arms, legs, fingers, and toes amount of vitamin B6 by mouth for 2 days take a final, larger amount of vitamin B6. Brain: • Abnormally curved spine (scoliosis) in a row. 6. Your blood homocysteine and methionine • Learning problems and developmental delays, • Brittle or weak bones (osteoporosis) 2. Two days after your first dose, your blood levels will be measured a final time for such as being slow to sit up, walk, or talk – homocysteine and methionine levels will Blood: the test. common early symptoms in children be measured again. • Behavioral problems, such as anxiety • Development of blood clots in veins 3. If no significant change has occurred, and depression or arteries that can obstruct blood flow. These may occur in the arms, you will take a larger amount of vitamin B6 • Seizures for 2 days in a row. legs, brain (resulting in stroke), • Increased risk of strokes (from blood clots or lungs (resulting in pulmonary developing in the brain or traveling to the brain) embolism) Test results Eyes: Vitamin B6-responsive Partially vitamin B6- Vitamin B6-non-responsive • Near-sightedness (often severe) – The medical term for or pyridoxine-responsive responsive or partially or pyridoxine-non-responsive a common and early symptom in children a blood clot is thrombus.
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