Question 1

A 12-year-old boy with Marfan syndrome complains to his nurse-practitioner, "My mother won't let me play football or do anything else. Isn't there something Ican do besides sitting and playing video games?" Which of the following activities may be considered less risky for this child to perform? Select all that apply.

Accepted Answer

A balance of physical activity is needed to be physically fit without placing strain on the cardiovascular system. Strenuous exercise and heavy lifting must be avoided, as should any activity in which the chest could be hit. Thus, contact sports and those that involve running or catching a ball should be avoided. Walking is encouraged, as are less physically aggressive sports, such as golfing, bowling, recreational swimming, or low-intensity bicycling. Competitive swimming is too intense.

Question 2

Which health problem could be expected as a result of a gene mutation that affects the correct production and function of type 1 collagen?

Accepted Answer

Type 1 collagen is a major component of bones, the dermal layer of skin, tendons, ligaments, corneas, intervertebral disks, and the walls of arteries and other blood vessels. It is critical in providing strength to blood vessel walls. With insufficient or poor-quality type 1 collagen, these blood vessel walls are flabby and can balloon out and rupture.

Question 3

A son with osteogenesis imperfecta is born to parents with no family history of the disease. What is the most likely explanation for the son's disorder?

Accepted Answer

There are four major types of osteogenesis imperfecta that occur as results of mutations in a gene for type 1 collagen. All follow an autosomal-dominant transmission pattern, although spontaneous mutations are responsible about 35% of the time.

Question 4

Couples from which ethnic group would derive the greatest benefit from genetic testing for Tay-Sachs disease?

Accepted Answer

The incidence of Tay-Sachs disease is highest among people of Ashkenazi Jewish ethnicity worldwide (1 in 3,900 births). The incidence among all other non-Jewish populations is much less frequent, about 1 in 320,000 births. French Canadians from Quebec have a higher incidence of Gaucher disease than the general population, but not of Tay-Sachs disease.

Question 5

Which clinical manifestation in a 6-month-old infant is most diagnostic for Tay-Sachs disease?

Accepted Answer

During the first few months of life, the infant with Tay-Sachs disease progresses normally, learning to control the head, recognize parental faces, socially smile, and roll over. At this point, normal development slows or stops, and physical development and cognitive development regress. The retinal cells have filled with GM2 and become pale. This makes the fovea centralis stand out as a cherry red spot against the pale retinal background. This is a hallmark of the disease. Although cognitive ability regresses over time, this is not limited to Tay-Sachs disease. Anemia and hepatosplenomegaly are not common manifestations of the disorder.

Question 6

Which manifestation is most common among individuals with osteogenesis imperfecta type I?

Accepted Answer

The clinical manifestations of osteogenesis imperfecta type I are relatively mild and can easily be missed because the collagen produced is normal, but the amount is reduced. Usually, the person has no increase in fractures during infancy. Fractures of long bones do occur in response to relatively minor trauma throughout childhood, adolescence, and adulthood, although the skull is not often involved. In women, more fractures are seen after menopause. The most common feature is the blue-tinged coloration of the sclerae.

Question 7

What is the most common cause of death among individuals with vascular Ehlers-Danlos (Ehlers-Danlos type IV)?

Accepted Answer

Vascular Ehlers-Danlos is severe and leads to premature death. The individual has very thin, fragile skin and short stature. Problems are associated with the thin connective tissue in mid-sized and large arteries, as well as in the intestinal tract. All of these tissues become thinner as the child grows. The most common causes of death are hemorrhage from arterial rupture and sepsis from intestinal rupture, often before the age of 30.

Question 8

The mother of a teenager recently diagnosed with osteogenesis imperfecta type I (OI) asks if the problem is related to the fact that she adhered to a vegetarian diet during pregnancy. What is the most appropriate response?

Accepted Answer

The primary problem with OI is failure to produce at least one functional chain of procollagen that is needed to associate with other molecules and form functional collagen in bone tissue. As a result, the developing bones have less structural integrity and strength, increasing the risk for fractures. The problem is a mutation in the gene coding for type 1 collagen. It is inherited in an autosomal-dominant transmission pattern, although spontaneous mutations are responsible about 35% of the time. Diet during pregnancy does not affect the development of the disorder in a fetus who has the gene mutation.

Question 9

Which manifestation in a teenage boy whose mother is a carrier for Fabry disease suggests the boy may have the disorder?

Accepted Answer

The onset of signs and symptoms usually begins later in childhood. At first, symptoms are related to poor perfusion and include cold intolerance, insufficient sweating in hot environments, and pain episodes of unknown origin. In adolescents, the symptoms worsen, with opacities developing in the eye. Deafness often occurs, not hyperacute hearing. Height is not affected or is shorter than that of unaffected siblings. Diabetes is not commonly associated with the disorder.

Question 10

Which substance fails to form normally in individuals with Marfan syndrome?

Accepted Answer

Marfan syndrome (MFS) is an inherited genetic connective tissue disorder in which the gene for the glycoprotein fibrillin is mutated. The collagen and elastin produced are normal, although the recoil strength of tissues during and after stretching is not normal because healthy fibrillin is not present to interact with the collagen and elastin. The structure and function of glycogen are not affected by the gene mutation that causes Marfan syndrome.

Quiz 10: Enzyme and Collagen Disorders