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The Smiths had just given birth to their second child and were eagerly waiting to take the newborn home. At that moment, their obstetrician walked into the hospital room with some news about their daughter’s newborn screening tests. The physician told them that the state’s mandatory newborn screening test had detected an abnormally high level of phenylalanine in their daughter’s blood. The Smiths asked if this was just a fleeting effect, like newborn jaundice, that would “go away” in a few days. When they were told that that was unlikely, they were even more confused. The pregnancy had progressed without any complications, and their daughter was born looking perfectly “normal.” Mrs. Smith even had a normal amniocentesis early in the pregnancy. The physician asked a genetic counselor to come to their room to explain their daughter’s newly diagnosed condition. The counselor began her discussion with the Smiths by taking a family history from each of them. She explained that phenylketonuria (PKU) is a genetic condition that results when an individual inherits an altered gene from each parent. The counselor wanted to make this point early in the session in case either parent attempted to cast blame for their daughter’s condition. She explained that PKU is characterized by an increased concentration of phenvlalanine in blood and urine and that intellectual disability can be part of this condition if it is not treated at an early age. To prevent the development of intellectual disability, after early diagnosis, dietary therapy must begin before the child is 30 days old. The newborn needs to follow a special diet in which the bulk of protein in the infant’s formula is replaced by an artificial amino acid mixture low in phenylalanine. The child must stay on this diet indefinitely for it to be maximally effective. PKU is one of several diseases known as the hyperphenylal-aninemias, which occur with a frequency of 1 in 10,000 births. Classic PKU accounts for two-thirds of these cases. PKU is an autosomal recessive disorder that is distributed widely among whites and Asians but is rare in blacks. Heterozygous carriers do not show symptoms but may have slightly increased phenylalanine concentrations. If untreated, children with classic PKU can experience progressive intellectual disability, seizures, and hyperactivity. EEG abnormalities; mousy odor of the skin, hair, and urine; a tendency to have light-colored skin; and eczema complete the clinical picture. Assume that you are the genetic counselor. How would you counsel the parents to help them cope with their situation if one or both were blaming themselves for the child's condition?

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Human Heredity: Principles and Iss...

11th Edition
Michael Cummings
Publisher: Cengage Learning
ISBN: 9781305251052

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Section
BuyFindarrow_forward

Human Heredity: Principles and Iss...

11th Edition
Michael Cummings
Publisher: Cengage Learning
ISBN: 9781305251052
Chapter 3, Problem 2CS
Textbook Problem
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The Smiths had just given birth to their second child and were eagerly waiting to take the newborn home. At that moment, their obstetrician walked into the hospital room with some news about their daughter’s newborn screening tests. The physician told them that the state’s mandatory newborn screening test had detected an abnormally high level of phenylalanine in their daughter’s blood. The Smiths asked if this was just a fleeting effect, like newborn jaundice, that would “go away” in a few days. When they were told that that was unlikely, they were even more confused. The pregnancy had progressed without any complications, and their daughter was born looking perfectly “normal.” Mrs. Smith even had a normal amniocentesis early in the pregnancy. The physician asked a genetic counselor to come to their room to explain their daughter’s newly diagnosed condition.

The counselor began her discussion with the Smiths by taking a family history from each of them. She explained that phenylketonuria (PKU) is a genetic condition that results when an individual inherits an altered gene from each parent. The counselor wanted to make this point early in the session in case either parent attempted to cast blame for their daughter’s condition. She explained that PKU is characterized by an increased concentration of phenvlalanine in blood and urine and that intellectual disability can be part of this condition if it is not treated at an early age.

To prevent the development of intellectual disability, after early diagnosis, dietary therapy must begin before the child is 30 days old. The newborn needs to follow a special diet in which the bulk of protein in the infant’s formula is replaced by an artificial amino acid mixture low in phenylalanine. The child must stay on this diet indefinitely for it to be maximally effective.

PKU is one of several diseases known as the hyperphenylal-aninemias, which occur with a frequency of 1 in 10,000 births. Classic PKU accounts for two-thirds of these cases. PKU is an autosomal recessive disorder that is distributed widely among whites and Asians but is rare in blacks. Heterozygous carriers do not show symptoms but may have slightly increased phenylalanine concentrations. If untreated, children with classic PKU can experience progressive intellectual disability, seizures, and hyperactivity. EEG abnormalities; mousy odor of the skin, hair, and urine; a tendency to have light-colored skin; and eczema complete the clinical picture.

Assume that you are the genetic counselor. How would you counsel the parents to help them cope with their situation if one or both were blaming themselves for the child's condition?

Summary Introduction

To predict: The treatment strategies for phenylketonuria (PKU).

Introduction: Phenylketonuria is a recessive disorder that mainly affects the Caucasian and the Asians. The diseases are marked by increased levels of phenylalanine in the blood which can result in intellectual disability and other physiological problems.

The case study describes a couple who have given birth to a second child and are informed about their newborn daughter’s genetic screening tests. The genetic tests indicated abnormally high levels of amino acid phenylalanine in the blood. Phenylketonuria (PKU) also known as hyperphenylalaninemia.

This occurs 1 in every 10,000 births. The classic form of PKU constitutes to 2/3rd of the cases. It is an autosomal recessive disorder implying that both the alleles of the patient are affected. When untreated it can lead to intellectual disability, seizures, and hyperactivity. The EEG shows abnormality along with the prominent mousy odor of skin, hair, and urine.

Explanation of Solution

The genetic counselor advises the parents of the developing fetus about the genetic anomalies that might occur during the development of the fetus. This is important as it aids in early detection and treatment (if any) or management of genetic disease. It can also help the parents to decide if they want to continue with the birth of the child who is developing a genetically fatal disease. PKU is a recessive disorder implying that the defective genes of both the parents inherited into the offspring result in the development of the disease.

The genetic diseases cannot be predetermined as there is always reshuffling when the genes are passed from parents to offsprings...

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Chapter 3 Solutions

Human Heredity: Principles and Issues (MindTap Course List)
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