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Detailed Definition PPA is a condition that occurs when the body lacks an enzyme needed to break down (metabolize) protein. When this enzyme is missing, parts of the protein build up in the body and cause damage to the nervous system, especially the brain. If left untreated, PPA can result in vomiting, anorexia, cardiac problems, blood disorders, failure to thrive, develomental delays, mental retardation, and even death. |
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Everyone needs protein for growth and repair of body tissues, but the body cannot use the protein in food until it is broken down (metabolized) into smaller parts. These “smaller parts” of protein are called amino acids. In PPA, four of these amino acids cannot be broken down (metabolized). These four amino acids are called: (1) isoleucine, (2) methionine, (3) threonine, and (4) valine. They should be broken down by an enzyme called Propionyl-CoA carboxylase (PCC). In people with PPA the PCC enzyme is either missing or does not work well. As a result, these amino acids cannot be metabolized properly causing Propionic Acid (PPA) to build up in the blood and damage the body, especially the brain. People with PPA also have trouble metabolizing several types of fatty acids (specifically, these include some of the odd-chain and polyunsaturated fatty acids).
PPA is an inherited disorder. The mode of inheritance is called "autosomal recessive", meaning that each parent carries a gene for the disorder that is passed on to the baby. PPA is caused by a malfunction in a pair of genes. Genes give the body the instructions it needs for growth and healthy development. They come in pairs and a baby receives one copy of each gene from the mother and one from the father. Everyone has some genes that have the potential to cause serious disease. Whether they do or not is beyond human control. There is nothing any parent can do to cause or prevent a change in a gene. "Autosomal" means that the condition can affect both males and females. "Recessive" means that the person with the disorder has two copies of the malfunctioning gene: one from the mother and one from the father. Although each parent carries one of these malfunctioning genes, they do not have the disorder themselves. This is because they each also carry a functioning gene, and this one gene, on its own, is able to keep their metabolism working normally. The malfunctioning gene is called the "recessive" gene because the functioning gene masks its presence. People with one functioning and one malfunctioning gene are considered to be "carriers" for the condition. When both parents are carriers for a metabolic condition, there is a 1 out of 4 chance (25%) that they will both pass on the recessive gene and have an affected child. If only one parent passes along the recessive gene, the child will be unaffected, but will be a carrier for the condition like the parents. The chance of this happening is 2 out of every 4 pregnancies (50%). And finally, the child may inherit neither of the recessive genes and will neither have the condition nor be a carrier. The chance of this happening is 1 out of every 4 pregnancies (25%). It is important to understand that carrier parents will have the same risks for each pregnancy regardless of how many affected or unaffected children they have previously had. For example, carrier parents who have had two affected children have the same chance in their third pregnancy of having an affected child as carrier parents who have two unaffected children. The risk is always 1 in 4 (25%).
Diagnosis: Infants, children and even adults that exhibit symptoms of PPA can be identified with a simple blood test that measures the amount of PPA in the blood. Further testing measuring the amount and type of enzyme activity is done to confirm the diagnosis. Through early detection and prompt treatment, many serious effects of PPA can be prevented.
The goal of PPA treatment is to keep the level of PPA in the blood as low as possible in order to avoid any of the poor consequences of having high levels. The treatment itself consists of four main parts: diet, formula, supplements, monitoring. 1. Diet: Please keep in mind that when we refer to "eating" that this includes any eating, drinking, swallowing, and chewing. When we refer to "foods," this includes all foods, drinks, medications, and even gum. The first aim in treatment is to cut down on the amount of protein that the person eats. This means that people with PPA must learn what types of foods are highest in protein and limit these foods. Some examples of foods high in protein include all types of meat (e.g., chicken, pork, beef, seafood), all types of dairy (e.g., milk, yogurt, cheese, whipped cream, ice cream, etc.), all types of beans and nuts (e.g., soybeans, pinto beans, peanuts, etc.), and eggs. People with PPA must also learn what foods have some amount of protein and ways to measure how much. Each individual, depending on the severity of their disorder, is given a daily limit of the protein they can eat. It is okay for people with PPA to eat some protein because, unlike an allergy, the protein will not cause them to have an “allergic” reaction. In fact, people with PPA must eat some protein every day as everyone needs some (1) isoleucine, (2) methionine, (3) threonine, and (4) valine for growth and development. The trick is not to eat too much. This is done by learning to count and keep track of the amount they consume throughout the day. One of the main problems in following the PPA diet is nutritional balance. Foods that are low in protein tend to be high in either fat or sugar or both. While some low-protein foods can be very nutritious, such as low-protein vegetables and fruit, others offer mostly “empty” calories. Foods that are high in empty calories supply a person with calories, but little nutrition. These calories are often needed for energy and growth but, when consumed in large amounts, can lead to obesity. Another problem is creating enough variety in the diet, especially for picky eaters. One way to increase variety is to eat low-protein specialty products. For instance, instead of avoiding all breads, pastas, and rice (which often have too much protein), people with PPA can try some of the special low-protein versions of these foods. There are also many other types of low protein foods available, such as cheese, peanut butter, pizza, etc. As of July 2000, California State law (Senate Bill #148) requires all health insurance companies to provide low-protein specialty foods free of charge to all patients with a condition called PKU. Kaiser Permenente has expanded this requirement to include patients with any metabolic condition requiring a low-protein diet. The Regional Metabolic Clinic has contracted with several different specialty food companies to provide these products. In order not to be charged for these products, patients must fill out RMC order forms and return them to the clinic for review and approval. The coordinators will then forward these forms on to the company(ies) and the food will be delivered directly to the patient’s home. Limit: $2500 per patient per year. 2. Formula The second part of the treatment for PPA requires a special protein formula. PPA formulas are special because they contain all the amino acids a person needs, but is limited in (1) isoleucine, (2) methionine, (3) threonine, and (4) valine. It is almost impossible to get enough protein to stay healthy on a PPA diet alone. Therefore, people with PPA need to drink formula in order to get enough of the protein without too much (1) isoleucine, (2) methionine, (3) threonine, and (4) valine. They are also fortified with essential vitamins and minerals. Fortunately, today there are several different PPA formulas to choose from. 3. Supplements a. Biotin b. Carnitine c. Isoleucine d. Valine 4. Monitoring The final part of the treatment for PPA is monitoring, in order to know whether the other three parts of the treatment (diet, formula, supplements) are actually working to keep the level of PPA as low as possible as well as maintain normal levels of (1) isoleucine, (2) methionine, (3) threonine, and (4) valine. It is best to find this out before the person with PPA experiences any of the possible bad effects (as discussed above). Monitoring is done by testing the levels of PPA as well as all the amino acids in the blood on a regular basis. The blood samples are drawn through a needle at the hospital lab and sent down to the Metabolic Laboratory at Kaiser in Los Angeles for testing. It can take several days to a week to receive the results. Other tests for monitoring PPA can include: Please note: not all these tests are done with every set of labs. For all blood tests, a 3-day diet record is recommended. To complete a diet record all the food eaten over the period of three days must be written down along with the amount eaten. The blood test(s) should be taken on the 4th day, right after the diet record is completed. The diet record is an important part of interpreting the test results. For instance, if the PPA level is high, is it because the person is eating too much protein or too little? It is hard to get an accurate picture of what is happening inside the body without having the information provided by the diet record. b. Other tests:
1. Low Protein Cookery for PKU (Please note:
this book is helpful for all low-pro diets.) 2. The Complete IEP Guide published by Nolo Press 3. How to Teach Nutrition to Kids 4. Positive Discipline 5. Positive Discipline: The First Three Years 6. Positive Discipline for PreSchoolers 7. Positive Discipline for Teenagers 8. Positive Time Out and 50 Other Ways to Avoid Power Struggles
in Homes and Classrooms 9. Social Security Disability: Getting & Keeping Your
Benefits published by Nolo Press 10. Temperament Tools: Working with Your Child’s Inborn
Traits 11. We're Different, We're the Same by Bobbi J. Kates. Illustrated
by Joe Mathieu. 12. Why Can't I Eat That!: Helping Kids Obey Medical Diets |
