Question 1

Neonatal vomiting and diarrhea and failure to thrive, combined with jaundice, hepatomegaly, early development of cataracts, and mental retardation, suggest the diagnosis of

Accepted Answer

Galactosemia, a mutation of the gene encoding galactose-phosphate-uridyl transferase, is characterized by growth retardation and digestive problems, as well as pathologic changes in the liver, eyes, and brain.

Question 2

Splenomegaly and skeletal changes due to a nonlethal lysosomal storage disease caused by the mutation of the gene encoding glucocerebrosidase are features of which disease?

Accepted Answer

Gaucher disease is caused by a mutation of the gene encoding glucocerebrosidase. In the most common of the three forms of Gaucher disease, which accounts for 99% of all cases, there is splenomegaly, lymphadenopathy, involvement of the bone marrow, and skeletal changes.

Question 3

Which one of the following parameters portends a good prognosis in patients with neuroblastoma?

Accepted Answer

Young age is a good prognostic factor and is associated with high curability of neuroblastomas. All patients younger than 1 year of age have an excellent prognosis, irrespective of the stage of the tumor. All other parameters listed have adverse prognostic implications.

Question 4

A 7-year-old child complained of frequent muscle cramps during play. A muscle biopsy revealed accumulation of glycogen in the skeletal muscle cells and a lack of muscle phosphorylase. Which form of glycogenosis is this?

Accepted Answer

Type V glycogenosis, also known as McArdle disease, is caused by muscle phosphorylase deficiency. Patients present with muscle cramps. In these patients, the blood level of lactic acid does not rise after exercise, because the enzyme deficiency prevents anaerobic glycolysis in the muscle cells.

Question 5

Which is the most common solid malignant tumor in children younger than the age of 1 year?

Accepted Answer

Neuroblastomas represent the most common solid malignant tumor in children younger than 1 year of age. Approximately 500 new cases are diagnosed each year in the United States.

Question 6

An infertile woman was examined cytogenetically and was found to have deletions of portions of the long arm and short arm of the chromosome X, resulting in a ring chromosome, 46,X,r(X). Which of the following is the most likely diagnosis?

Accepted Answer

A ring chromosome, 46,X,r(X), is found in patients with Turner syndrome. Such patients are in a minority, since most patients with Turner syndrome (57%) actually have a 45,X karyotype and lack one of the two X chromosomes.

Question 7

Overall, which of the following is the most common malignancy found in children younger than 4 years of age?

Accepted Answer

Leukemia, which most often occurs in the form of acute lymphoblastic leukemia, is the most common form of malignancy in infants and in children younger than 4 years of age.

Question 8

In which of the following Mendelian disorders is the age of onset delayed and the symptoms of the disease do not appear before adulthood?

Accepted Answer

Symptoms of Huntington disease, which include chorea and mental deterioration, are typically delayed and do not appear before adulthood.

Question 9

Which disease is caused by prolonged exposure of premature infants to oxygen at a high concentration?

Accepted Answer

Retrolental fibroplasia is a well-known ocular complication of prolonged exposure of neonates to a high concentration of oxygen in incubators.

Question 10

Which hormone can suppress surfactant production in fetal lungs?

Accepted Answer

Insulin is known to suppress surfactant production in fetal lungs. High levels of insulin in diabetic mothers, who are resistant to insulin action, are an important cause of fetal pulmonary immaturity, predisposing premature infants of diabetic mothers to neonatal respiratory distress syndrome.

Question 11

Which of the following diseases is caused by a trinucleotide repeat mutation?

Accepted Answer

Fragile X syndrome is caused by a trinucleotide repeat mutation of the long arm of the X chromosome. Patients with the disease present with mental retardation and enlarged testes.

Question 12

Chromosome 22q11 deletion is typically associated with

Accepted Answer

Chromosome 22q11 deletion is found in children who have DiGeorge syndrome and velocardiofacial syndrome. These two syndromes are known to be closely related and are known as the CATCH 22 syndrome (cardiac abnormalities, anomalous facial features, thymic hypoplasia with T-cell deficiencies, clef palate, and hypocalcemia due to hypoparathyroidism resulting from chromosome 22q11 deletion).

Question 13

Which malignancy occurs at a high rate in persons affected with Down syndrome?

Accepted Answer

Children with Down syndrome are at a 10 to 20-fold higher risk of developing acute lymphoblastic leukemia or acute myelogenous leukemia than are their age-matched controls.

Question 14

The soft core of an aortic atheroma consists primarily of

Accepted Answer

The soft core of atheromas consists predominantly of cholesterol. Cholesterol crystals in routine histologic sections appear like empty narrow rhomboid clefts, because alcohol and xylene used during processing dissolve and remove cholesterol from the tissues.

Question 15

Mutation of the gene for lysyl hydroxylase in the kyphoscoliosis type Ehlers-Danlos syndrome (ED type VI) causes weakness of bones and cutis laxa because of abnormal collagen

Accepted Answer

Lysyl hydroxylase is an enzyme that is essential for cross-linking of collagen. Without it, the collagen never achieves full structural integrity and strength; accordingly, the bones are weak and prone to deformation, whereas the skin becomes hyperextensible ("cutis laxa").

Question 16

Most teratomas in infants are located in the

Accepted Answer

Most congenital teratomas are located in the sacrococcygeal region, and appear as masses attached to the "rump."

Quiz 6: Genetic and Pediatric Diseases