Patho PrepU Ch. 5 (Genetic and Congenital Disorders)

A pregnant client's α-fetoprotein (AFP) returns elevated. The couple ask the health care worker to explain what this means. Which is the best response?

"Elevated AFP means your baby is at risk of having a neural tube defect like spina bifida (an opening in the spine)." Explanation: Maternal and amniotic fluid levels of AFP are elevated in pregnancies where the fetus has a neural tube defect (i.e., anencephaly and open spina bifida) or certain other malformations such as an anterior abdominal wall defect in which the fetal integument is not intact. Screening of maternal blood samples usually is done between weeks 16 and 18 of gestation. Although neural tube defects have been associated with elevated levels of AFP, decreased levels have been associated with Down syndrome.

The nurse is providing education to the parent of a male diagnosed with Marfan syndrome. The nurse knows that her teaching has been effective when the parent states which of the following?

"His participation in sports may need to be limited." Explanation: Marfan syndrome affects several organ systems, including the eyes, cardiovascular, and skeletal systems. The risks associated with participation in sports depend on which organ system is involved. There is no cure for Marfan syndrome and the most life-threatening aspects of the disorder are the cardiovascular defects.

The parents of a newborn are relieved that their baby was born healthy, with the exception of a cleft lip that will be surgically corrected in 10 to 12 weeks. Which statement by the nurse to the parent's best conveys the probable cause of the newborn's cleft lip?

"Your newborn's cleft lip likely results from the interplay between environment and genes." Explanation: A cleft lip is considered to be a multifactorial disorder, in which both environment and genes contribute to the condition. It does not depend solely on Mendelian patterns of inheritance. A cleft lip is not known to result from teratogenic drugs.

The health care provider informs the client that she is at risk for developing an autosomal recessive disorder. For which disorder may the client be at risk?

Tay-Sachs disease Explanation: Tay-Sachs disease is the only one of these diseases that is an autosomal recessive disorder. All the others are autosomal dominant disorders.

A pregnant client is just completing her first trimester and has opted for alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) testing. The nurse should identify what implication from this client's decision?

The client wishes to know about her fetus' risk of having a trisomy. Explanation: AFP and hCG testing are most often performed to determine the risks of a trisomy. Multifactorial disorders are not revealed by this form of testing and the nurse should not presume that the client will choose to have an abortion if the results are positive. The use of AFP and hCG testing does not preclude the use of amniocentesis.

The nurse is caring for a client who tried to become pregnant but suffered a spontaneous abortion (miscarriage) during her first trimester. What is the most likely etiology of the client's abortion?

The fetus had a chromosomal disorder. Explanation: Chromosomal abnormalities are thought to cause around half of first-term abortions. For most women, this possibility is a much more likely cause of abortion than radiation or toxins. X-linked disorders are not thought to be a major cause of spontaneous abortion.

A person's genotype can best be described as which of the following?

The genetic makeup of an individual Explanation: The genetic makeup of an individual is known as a genotype. Phenotype is the observable expression of a genotype in terms of morphologic, biochemical, or molecular traits. If the trait is expressed in the heterozygote (one member of the gene pair codes for the trait), it is said to be dominant. If it is expressed only in the homozygote (both members of the gene pair code for the trait), it is recessive.

The pregnant client asks if there are any precautions she should take in caring for the family cat. The nurse explains that she should limit contact with the cat's litter box. The litter box may contain which organism that can cause fetal malformations?

Toxoplasmosis Explanation: The domestic cat can carry the organism Toxoplasma gondii, excreting the protozoa in its feces. It has been suggested that pregnant women should avoid contact with excrement from the family cat. The other options are infectious teratogenic agents, but are not carried by cats.

The provider is doing genetic counseling with a client. He explains that which condition affects only females?

Turner syndrome Explanation: Turner syndrome describes an absence of all (45, X/0) or part of the X chromosome and, as such, is seen only in females. Klinefelter syndrome is a condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the normal XY complement. Most males with Kleinfelter syndrome have one extra X chromosome (47, XXY). Down syndrome, trisomy 21, can be seen in either sex. Fragile X syndrome, as with other X-linked disorders, affects boys more often than girls.

The nurse is assessing a newborn. What characteristic finding makes the nurse suspect the newborn has trisomy 21?

Upward slanting of eyes Explanation: Newborns with Down syndrome have short stubby fingers and a single palmar crease (simian crease). The other distinctive features include upward slanting eyes, protruding tongue, and low-set little ears.

While examining a client, the practitioner notices large, flat, cutaneous pigmentations. They are a uniform light brown with sharply demarcated edges. He uses a Wood lamp to better detect the lighter spots. The practitioner knows that the pigmentations may be a component of which disorder?

Von Recklinghausen disease Explanation: A second major component of type 1 neurofibromatosis, or von Recklinghausen disease, is the presence of large, flat cutaneous pigmentations known as café au lait spots. A Wood lamp, which uses ultraviolet light, can be used to detect lighter spots. The other options are chromosomal disorders and do not exhibit these pigmentations.

A nurse is teaching a pregnant client about teratogenic drugs. Which drug category will the nurse emphasize for the client to avoid during pregnancy?

X Explanation: This system classifies all drugs approved after 1983 into five pregnancy risk categories: A, B, C, D, and X. Drugs in category A are the least dangerous, and categories B, C, and D are increasingly more dangerous. Those in category X are contraindicated during pregnancy because of proven teratogenicity.

A client goes to radiology for a series of x-rays. As the lead apron is placed over the client, he asks why it is needed. The client should be told that the vest is to protect:

against chromosomal breakage. Explanation: X-rays have been shown to cause chromosomal breakage and lead to rearrangement and mutation; they do not directly affect the cytoplasm. Proteins and lipids may be altered by X-rays, but they are quickly degraded and removed and therefore have no effect.

The nurse is explaining congenital defects to a newly pregnant client. She explains that one of the most common birth defects is:

cleft lip with or without cleft palate. Explanation: Cleft lip with or without cleft palate is one of the most common birth defects. Other congenital defects that are thought to arise through multifactorial inheritance are clubfoot, congenital dislocation of the hip, congenital heart disease, pyloric stenosis, and urinary tract malformation.

Unlike other teratogens, alcohol exposure during pregnancy (fetal alcohol spectrum disorders) can have what harmful effect on the fetus?

developmental abnormalities throughout the prenatal and postnatal period Explanation: Unlike other teratogenic exposures that cause abnormalities during a short period of time during fetal development (usually in the early weeks), fetal alcohol spectrum disorders (FASD) damage the chromosomes of the developing fetus as long as alcohol continues to circulate through the fetal bloodstream. FASD is diagnosed by the presence of three findings that do not include liver abnormalities and are not life threatening. Facial features characteristic of FASD are most noticeable during childhood. The facial features of FASD may not be as apparent in older people. Each defect can vary in severity, probably reflecting the timing of alcohol consumption in terms of the period of fetal development, amount of alcohol consumed, and hereditary and other environmental influences.

A young man has been diagnosed with Huntington disease following several months of progressive muscle weakness. The man has two young children: one boy and one girl. The nurse should teach the man that:

each child has 50% chance of developing Huntington disease. Explanation: In a single-gene autosomal dominant disease such as Huntington, the affected parent has a 50% chance of transmitting the disorder to each offspring. Sex-linked differences do not exist.

The most critical time for teratogenic influence in embryonic development is:

from day 15 to day 60 after conception. Explanation: The embryo's development is most easily disturbed during the period when differentiation and development of the organs are taking place. This time interval, which is often referred to as the period of organogenesis, extends from day 15 to day 60 after conception.

Which health care provider is the highest priority for immediate assistance in the first 24 hours following the birth of a newborn with a cleft lip?

lactation consultant Explanation: Newborns with a cleft lip typically have difficulty with feeding, and the assistance of a lactation consultant may be of help in establishing feeding patterns. Oxygenation is not a typical problem, while activities of daily living and assistive devices are not relevant considerations. Although social work is often of assistance when a child is born with a congenital condition, a cleft lip has fewer implications than most other inherited disorders.

A nurse is caring for an infant born with a cleft lip and palate. The priority of care would address:

malnutrition. Explanation: The immediate problem in infants with cleft lip and palate is feeding because of their inability to suck to breast-feed or drink from a bottle. The others will be of concern at a later time and are not life threatening.

The nurse is studying genetic disorders. She learns that an allele is:

one of two members of a gene pair, for a particular trait, in a chromosome pair. Explanation: The two members of a gene pair, one inherited from the mother and the other from the father, are called alleles. The presence of more than two chromosomes to a set is called polysomy. The physical trait associated with a particular gene is the phenotype.

A mother who has one mutant allele on the X chromosome and one normal allele asks the nurse what the percentage is of passing it on to a daughter to be a carrier. The best response would be:

50% Explanation: The common pattern of inheritance is one in which an unaffected mother carries one normal and one mutant allele on the X chromosome. This means that she has a 50% chance of transmitting the defective gene to her sons, and her daughters have a 50% chance of being carrier of the mutant gene.

A newborn has been diagnosed with phenylketonuria (PKU). The nurse teaches the mother about a special diet to restrict phenylalanine intake. When does this diet need to be initiated?

7 to 10 days of age Explanation: Dietary treatment of PKU must be started early in neonatal life to prevent brain damage. Infants with elevated phenylalanine levels should begin treatment by 7-10 days of age.

Teratogenic substances cause abnormalities during embryonic and fetal development. These substances have been divided into three classes. These classes are called:

radiation; drugs and chemical substances; and infectious agents. Explanation: Teratogenic agents have been divided into three groups: radiation; drugs and chemical substances; and infectious agents. The period of organogenesis, the third trimester, and the second trimester are not teratogenic substances. They are time periods during the pregnancy. Teratogenic substances are not classified as outside, inside, or internal. Although drugs and chemical substances are a class of teratogenic agents, smoking is included in that class as a teratogenic agent. It is not a class unto itself. Bacteria and viruses are considered infectious agents and are therefore teratogenic agents.

Which statement is true about recessive gene inheritance?

A carrier is a nonaffected person with a single copy of a recessive gene. Explanation: Autosomal recessive disorders are manifested only when both members of the gene pair are affected. Therefore, a carrier is a nonaffected person with a single copy of a recessive gene. Dominant genes have greater expression than recessive ones. Because of the presence of a normal X gene, female heterozygotes rarely experience the effects of a defective gene, whereas all males who receive the gene are typically affected. Variability of gene expression is called variable expressivity.

A sonogram on a woman in the first trimester of her pregnancy shows abnormal fetal findings. The nurse prepares to provide the woman with information concerning which diagnostic procedure?

Amniocentesis Explanation: Amniocentesis is useful in women with elevated risk on first trimester screen or quad screen; abnormal fetal findings on sonogram; or in parents who are carriers or with a strong family history of an inherited disease. Chorionic villus sampling is an invasive diagnostic procedure that obtains tissue that can be used for fetal chromosome studies, DNA analysis and biochemical studies. Percutaneous umbilical cord blood sampling (PUBS) is used for prenatal diagnosis of hemoglobinopathies, coagulation disorders, metabolic and cytogenetic disorders, and immunodeficiencies. Biochemical analyses can be used to detect abnormal levels of AFP and abnormal biochemical products in the maternal blood and in specimens of amniotic fluid and fetal blood.

The nurse is studying numeric disorders involving autosomes. Which term refers to having an abnormal number of chromosomes?

Aneuploidy Explanation: Having an abnormal number of chromosomes is referred to as aneuploidy. When a person inherits a dominant mutant gene, but fails to express it, the trait is described as having reduced penetrance. In mitochondrial gene disorders, some cells receive a mixture of normal and mutant DNA, known as heteroplasmy. Occasionally, mitotic errors in early development give rise to two or more cell lines characterized by distinctive karyotypes, a condition referred to as mosaicism.

Marfan syndrome, which is a connective tissue disorder, affects several organ systems. The most life-threatening aspects of the disorder are caused by defects in which system?

Cardiovascular Explanation: Marfan syndrome affects several organ systems, including the cardiovascular, skeletal, and ocular systems. The most life-threatening aspects of the disorder are the cardiovascular defects, which include mitral valve prolapse, progressive dilation of the aortic valve ring, and weakness of the aorta and other arteries.

A woman gave birth to a small infant with a malformed skull. The infant grows slowly and shows signs of substantial cognitive and intellectual deficits. The child also has facial abnormalities that become more striking as it develops. What might the nurse expect to find in the mother's pregnancy history?

Chronic alcohol use Explanation: The infant's signs and symptoms are characteristic of fetal alcohol syndrome. Folic acid deficiency is associated with neural tube defects, such as anencephaly and spina bifida. Cocaine use is associated with some of the same signs and symptoms as alcohol use but does not produce the characteristic facial abnormalities of fetal alcohol syndrome. Herpes simplex infection, although it is associated with microcephaly, hydrocephalus, defects of the eye, and hearing problems, also does not produce characteristic facial abnormalities.

The nurse is preparing to administer a pregnant client's medication when it is noted that the client is prescribed tetracycline for an infection. The nurse should do which of the following?

Contact the physician Explanation: The nurse should contact the physician and request a different antibiotic as tetracylcine is a known teratogenic agent.

A pregnant woman's ultrasound reveals intrauterine growth retardation (IUGR) and a TORCH agent is thought to be the cause. Which nursing action is appropriate?

Determine whether the client has been immunized against rubella. Explanation: TORCH stands for toxoplasmosis, other, rubella (i.e., German measles), cytomegalovirus, and herpes. Hepatitis, tetanus, and cholera are not included among lists of TORCH agents.

The genetic counselor is explaining structural changes in chromosomes that result from breakage and rearrangement of chromosome parts. The pattern that occurs when there are simultaneous breaks in two chromosomes, from different pairs, with exchange of chromosome parts is:

translocation Explanation: Translocation occurs when there are simultaneous breaks in two chromosomes, from different pairs, with exchange of chromosome parts. Isochromosome formation occurs when the centromere, or central portion, of the chromosome separates horizontally instead of vertically. Ring formation results when deletion is followed by uniting of the chromatids to form a ring. Inversion requires two breaks on a single chromosome with inversion to the opposite side of the centromere or with the fragment inverting but remaining on the same arm.

With increasing age comes a greater chance of a woman having been exposed to damaging environmental agents such as drugs, chemicals, and radiation. These factors may act on the aging oocyte to cause which abnormality in a fetus?

Down syndrome Explanation: The risk of having a child with Down syndrome increases with maternal age—it is 1 in 1250 at 25 years of age, 1 in 400 at 35 years, and 1 in 100 at 45 years of age. The reason for the correlation between maternal age and nondisjunction is unknown, but is thought to reflect some aspect of aging of the oocyte. Although males continue to produce sperm throughout their reproductive life, females are born with all the oocytes they ever will have. These oocytes may change as a result of the aging process. With increasing age, there is a greater chance of a woman having been exposed to damaging environmental agents such as drugs, chemicals, and radiation. There is no correlation with maternal age and the other syndromes.

Maternal serum alpha-fetoprotein (AFP) is a screening test for which condition?

Down syndrome Explanation: There are several prenatal screening tests that can be done to determine the risk of having a child with Down syndrome. The most commonly used are blood tests that measure maternal serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol, inhibin A and pregnancy-associated plasma protein A (PAPP-A). AFP is not a screening test for the other conditions.

A pregnant client has just undergone cytogenetic studies to determine fetal karyotyping. She learns that her fetus has trisomy 21. Which of the following is a manifestation of this condition?

Epicanthal eye folds Explanation: A child with Down syndrome, or trisomy 21, has a flat facial profile, with a small nose and somewhat depressed nasal bridge; small folds in the inner corners of the eyes (epicanthal folds), and upward slanting of the eyes. The other responses are not seen in Down syndrome.

Which risk factor increases the chances of the development of a neural tube defect during embryonic development?

Folate deficiency Explanation: Folate deficiency has been closely linked as a risk factor for the development of neural tube defects because folate is needed for the synthesis of amino acids and DNA. It is now recommended that women take folic acid prior to conception to prevent neural tube defects.

After studying genetic disorders, the pathophysiology student knows that which of the following is true?

Genotype determines phenotype. Explanation: The genetic compostion of a person is called a genotype, whereas the phenotype is the observable expression of a genotype. Diabetes mellitus is caused by a multifactorial inheritance disorder and sickle cell anemia by a single gene defect. Many diseases caused by a single-gene defect have been identified.

The nurse assessing a client with Klinefelter syndrome would evaluate which signs as being expected findings? Select all that apply.

Gynecomastia Testicular atrophy Explanation: The nurse assessing a client with Klinefelter syndrome would evaluate the findings of gynecomastia and testicular atrophy as expected findings. However, excessive facial hair and decreased cognition would not be considered expected findings.

While teaching a preconception workshop for young adults, the nurse knows that the participants understand the educational teaching when they state which agents are teratogenic? Select all that apply.

Having a glass of wine with dinner Casual use of cocaine The use of warfarin Explanation: Even small amounts of alcohol consumed during critical periods of fetal development may be teratogenic. There is no evidence that diagnostic levels of radiation (from a chest x-ray) cause congenital abnormalities. Among drugs known to cause fetal abnormalities are cocaine and warfarin. Vitamin A and its derivatives have been targeted for concern of their teratogenic potential but not Vitamin D.

Which characteristic of genetic disorders involves a single-gene trait?

Mendelian patterns of inheritance Explanation: Single-gene disorders are characterized by patterns of transmission that follow the Mendelian patterns of inheritance. Multifactorial inheritance involves more than one gene mutation, rearrangement of groups of genes, and uneven numbers of some chromosomes in each cell.

A couple is scheduled to obtain familial lineage studies. The nurse is providing education. To which aspect of the DNA analysis should the woman pay particular attention regarding inherited disorders?

Mitochondrial DNA Explanation: Mitochondrial DNA is inherited maternally (i.e., from the mother) and provides a basis for familial lineage studies. Extrachromosomal DNA is used in the synthesis of mitochondrial RNAs and proteins used in oxidative metabolism. G-protein-linked receptors mediate cellular responses for numerous types of first messengers, including proteins, small peptides, amino acids, and fatty acid derivatives such as the prostaglandins.

A nurse confers with the attending physician about a client with encephalopathy who has been attributed to mitochondrial gene mutation. Why do mutations of the mitochondria affect the brain?

Mitochondrial mutations affect the ability of tissues to synthesize ATP, and tissues with high demands malfunction without enough ATP. Explanation: Tissues that have a high demand for the energy provided by ATP malfunction very quickly when ATP cannot be produced fast enough. This includes the brain, the muscular system, the auditory system, and the retina. Mitochondria cannot be silenced by the cell. Mitochondrial proteins and mutations can affect the cell where they reside but not the entire organ.

The tissue that is damaged in Huntington chorea is which of the following?

Nerve tissue Explanation: Huntington chorea is a neurodegenerative disorder. It does not involve the other types of tissue.

The nurse is teaching a class of pregnant woman about nutrition, emphasizing their need for folic acid. The nurse's rationale for this relates to prevention of which birth defect?

Neural tube defects Explanation: Folic acid deficiency has been implicated in the development of neural tube defects (anencephaly, spina bifida, encephalocele). Studies have shown a significant decrease in neural tube defects when folic acid was taken long term by women of reproductive age.

An adolescent presents at the clinic with reports of pedunculated lesions projecting from the skin on the trunk area. The nurse knows that this is a sign of:

Neurofibromatosis type 1 Explanation: In more than 90% of persons with neurofibromatosis type 1, cutaneous and subcutaneous neurofibromas develop in late childhood or adolescence. The cutaneous neurofibromas, which vary in number from a few to many hundreds, manifest as soft, pedunculated lesions that project from the skin. Marfan syndrome affects several organ systems, including the ocular system (eyes), the cardiovascular system (heart and blood vessels), and the skeletal system (bones and joints). Down syndrome is a congenital condition characterized by varying degrees of intellectual disability and multiple defects. Klinefelter syndrome is a condition that occurs in men who have an extra X chromosome in most of their cells. The syndrome can affect different stages of physical, language, and social development. The most common symptom is infertility.

A nurse caring for a client with a genetic disorder of mitochondrial DNA assesses for abnormalities in which body system?

Neuromuscular Explanation: Mitochondrial DNA disorders, although rare, affect the tissues of the neuromuscular system.

Which microorganism can cross the placenta and enter the fetal circulation causing the most frequent fetal anomalies?

Rubella Explanation: TORCH stands for toxoplasmosis, other, rubella (German measles), cytomegalovirus, and herpes. This acronym can be used to remember the agents most frequently implicated in fetal anomalies. Strept thorat, common colds, and the flu can cause concern for the mother but rarely result in fetal anomalies.

The parents of an infant boy ask the nurse why their son was born with a cleft lip and palate. The nurse responds that cleft lip and palate are defects that are caused by many factors. The defect may also be caused by teratogens. Which teratogens can cause cleft lip and palate?

Rubella Explanation: This defect may be caused by the teratogen rubella and is often encountered in children with chromosomal abnormalities.

Which health problem may be identified by a TORCH screening test?

Rubella and herpes Explanation: The acronym TORCH stands for toxoplasmosis, other, rubella (i.e., German measles), cytomegalovirus, and herpes, which are the agents most frequently implicated in fetal anomalies. The TORCH screening test examines the infant's serum for the presence of antibodies to these agents.

Select the screening procedure performed on newborns to decrease the risk of intellectual disability and compromised neurological development.

Serum phenylalanine test Explanation: Newborn infants are routinely screened within 12 hours of birth for abnormal levels of serum phenylalanine to detect high levels that could cause irreversible intellectual disability. The other procedures that may be performed after birth would not be used as a screening tool for intellectual disability.

The physician suspects a client may have Klinefelter syndrome. To confirm the diagnosis, the chromosome pattern would identify:

47, XXY Explanation: Most males with Klinefelter syndrome have one extra X chromosome (47, XXY), and in rare cases, there may be one additional extra X chromosome (48, XXXY).