Inherited metabolic disorders are genetic conditions that result in metabolism problems. Most people with inherited metabolic disorders have a defective gene that results in
an enzyme deficiency. There are hundreds of different genetic metabolic disorders, and their symptoms, treatments, and prognoses vary widely. Metabolism refers to all the chemical reactions taking place in the body to convert or use energy. A few major examples of
metabolism include: Metabolism is an organized but chaotic chemical assembly line. Raw materials, half-finished products, and waste materials are constantly being used, produced, transported, and excreted. The "workers" on the assembly line are enzymes and other proteins that make chemical reactions happen. In most inherited metabolic disorders, a single enzyme is either not produced by the body at all or is produced in a form that doesn't work. The missing enzyme is like an absentee worker on the assembly line. Depending on that enzyme's job, its absence means toxic chemicals may build up, or an essential product may not be produced. The code or blueprint to produce an enzyme is usually contained on a pair of genes. Most people with inherited metabolic
disorders inherit two defective copies of the gene -- one from each parent. Both parents are "carriers" of the bad gene, meaning they carry one defective copy and one normal copy. In the parents, the normal gene copy compensates for the bad copy. Their enzyme levels are usually adequate, so they may have no symptoms of a genetic metabolic disorder. However, the child who inherits two defective gene copies cannot produce enough effective enzyme and develops the genetic metabolic disorder.
This form of genetic transmission is called autosomal recessive inheritance. The original cause of most genetic metabolic disorders is a gene mutation that occurred many, many generations ago. The gene mutation is passed along through the generations, ensuring its preservation. Each inherited metabolic disorder is quite rare in the general population. Considered all together, inherited metabolic disorders may affect about 1 in 1,000 to 2,500 newborns. In certain ethnic populations,
such as Ashkenazi Jews (Jews of central and eastern European ancestry), the rate of inherited metabolic disorders is higher. Hundreds of inherited metabolic disorders have been identified, and new ones continue to be discovered. Some of the more common and important genetic metabolic disorders include: Lysosomal storage disorders: Lysosomes are spaces inside cells that break down waste products of metabolism. Various enzyme deficiencies inside lysosomes can result in buildup of toxic substances, causing metabolic disorders including: Galactosemia: Impaired breakdown of the sugar galactose leads to
jaundice, vomiting, and liver enlargement after
breast or formula feeding by a newborn. Maple syrup urine disease: Deficiency of an enzyme called BCKD causes
buildup of amino acids in the body. Nerve damage results, and the urine smells like syrup. Phenylketonuria (PKU): Deficiency of the enzyme PAH results in high levels of phenylalanine in the
blood. Intellectual disability results if the condition is not recognized. Glycogen storage diseases: Problems with sugar storage lead to low blood sugar levels, muscle pain, and weakness. Mitochondrial disorders: Problems inside mitochondria, the powerhouses of cells, lead to muscle damage. Friedreich ataxia: Problems related to a protein called frataxin cause nerve damage and often heart problems. Inability to walk usually results by young adulthood. Peroxisomal disorders: Similar to lysosomes, peroxisomes are tiny spaces filled with enzymes inside cells. Poor enzyme function inside peroxisomes can lead to buildup of toxic products of metabolism. Peroxisomal disorders include:
Metal metabolism disorders: Levels of trace metals in the blood are controlled by special proteins. Inherited metabolic disorders can result in protein malfunction and toxic accumulation of metal in the body:
Organic acidemias:methylmalonic acidemia and propionic acidemia. Urea cycle disorders:ornithine transcarbamylase deficiency and citrullinemia The symptoms
of genetic metabolic disorders vary widely depending on the metabolism problem present. Some symptoms of inherited metabolic disorders include: The symptoms may
come on suddenly or progress slowly. Symptoms may be brought on by foods, medications, dehydration, minor illnesses, or other factors. Symptoms appear within a few weeks after birth in many conditions. Other inherited metabolic disorders may take years for symptoms to develop. Inherited metabolic disorders are present at birth, and some are detected by routine screening. All 50 states screen newborns for phenylketonuria (PKU). Most states also test newborns for galactosemia. However, no state tests babies for all known inherited metabolic disorders. Improved testing technology is leading many states to expand newborn screening for genetic metabolic disorders. The
National Newborn Screening and Genetics Resources Center provides information on each state's screening practices. If an inherited metabolic disorder is not detected at birth, it is often not diagnosed until symptoms appear. Once symptoms develop, specific blood or DNA tests are available to diagnose most genetic metabolic disorders. Referral to a specialized center (usually at a university) increases the chances of a correct diagnosis. Limited treatments are available for inherited metabolic disorders. The essential genetic defect causing the condition can't be corrected with current technology. Instead, treatments try to work around the problem with metabolism. Treatments for genetic metabolic disorders follow a few general principles:
Treatment may include such measures as:
Whenever possible, a person with an inherited metabolic disorder should receive care at a medical center with experience with these rare conditions. Children and adults with inherited metabolic disorders can become quite ill, requiring hospitalization and sometimes life support. Treatment during these episodes focuses on emergency care and improving organ function. What is the genetic disorder in which an essential digestive enzyme is missing quizlet?The genetic disorder in which an essential digestive enzyme is missing is known as phenylketonuria. The inflammation of a gland is known as adenitis. The parietal peritoneum is the outer layer of the peritoneum that lines the interior of the abdominal wall.
Which of the following is a genetic disorder in which the essential digestive enzyme phenylalanine hydroxylase is missing?Phenylketonuria (fen-ul-key-toe-NU-ree-uh), also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body. PKU is caused by a change in the phenylalanine hydroxylase (PAH) gene. This gene helps create the enzyme needed to break down phenylalanine.
What is also known as a hereditary disorder is a pathological condition caused by an absent or defective gene?A single-gene disorder (also called Mendelian disorder) is caused by a defect in one particular gene. Single gene defects are rare. But since there are many thousands of known single gene disorders, their combined impact is significant. Single-gene disorders are characterized by how they are passed down in families.
Which term describes increased growth or development of an organ or tissue that is not related to a tumor?Before cancer cells form in tissues of the body, the cells go through abnormal changes called hyperplasia and dysplasia. In hyperplasia, there is an increase in the number of cells in an organ or tissue that appear normal under a microscope. In dysplasia, the cells look abnormal under a microscope but are not cancer.
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