Pediatric Examination and Board Review (143 page)

SELECT THE ONE BEST ANSWER

1.
Immediate investigations should include a

(A) blood culture

(B) chest radiograph

(C) complete blood count

(D) computed tomography (CT) brain scan

(E) glucose measurement by glucose oxidase reagent strip

2.
The glucose oxidase reagent strip reveals a glucose of 30. The next most appropriate step in management is

(A) consult an endocrinologist for advice on how to evaluate the hypoglycemia

(B) intravenous dextrose 25% at a dose of 2-4 ml/kg

(C) oral glucose replacement with orange juice

(D) immediate intubation and mechanical ventilation

(E) call for newborn screen results

3.
When starting the intravenous (IV) for glucose replacement, which of the following laboratory investigations are important in determining the underlying etiology of the hypoglycemia?

(A) electrolytes, blood urea nitrogen (BUN), creatinine, plasma glucose, liver profile, complete blood count

(B) urine and/or serum ketones

(C) endocrinology labs including cortisol, insulin, C-peptide, growth hormone

(D) carnitine levels, acylcarnitine profile, urine organic acids, serum amino acids, and lactate level

(E) all of the above

4.
The initial results of the laboratory testing are as follows: sodium 139 mEq/L, potassium 4.5 mEq/L, chloride 107 mEq/L, bicarbonate 17 mEq/L, glucose 32 mg/dL, urine ketones negative, serum ketones negative, aspartate aminotransferase (AST) 257 U/L, alanine aminotransferase (ALT) 205 U/L. The remaining labs are unremarkable. The most likely diagnosis given this information is

(A) galactosemia

(B) hyperinsulinism

(C) medium chain acyl-CoA dehydrogenase (MCAD)

(D) physiologic ketotic hypoglycemia

(E) salicylate poisoning

5.
What other additional history or physical findings in this case are consistent with MCAD?

(A) prolonged period of poor appetite

(B) diaphoresis and lethargy

(C) family history of SIDS

(D) history of vomiting

(E) A and C

6.
How would you counsel the family about other siblings and the risk of MCAD for future children?

(A) siblings and future children are at 5% risk for MCAD

(B) siblings and future children are at 25% risk for MCAD

(C) siblings and future children are at 50% risk for MCAD

(D) siblings and future children are at less than 1% risk for MCAD

(E) only girls are at 50% risk; boys are not affected

7.
If this patient had hepatomegaly without splenomegaly, retarded growth, poorly developed musculature, hyperlipidemia, and hypercholesterolemia, the most likely diagnosis would be

(A) fatty acid oxidation defect

(B) glycogen storage disorder

(C) growth hormone deficiency

(D) insulin-induced hypoglycemia

(E) none of the above

8.
Which of the following symptoms would be suspicious for galactosemia as a cause of the hypoglycemia?

(A) vomiting and jaundice

(B)
Escherichia coli
sepsis

(C) hepatomegaly with elevated transaminases

(D) renal Fanconi syndrome

(E) all of the above

9.
All of the following regarding the long-term sequelae of galactosemia are true except

(A) patients may have deficits in speech and language

(B) sequelae may be present even if appropriate treatment is initiated early

(C) pseudotumor cerebri is a possible sequela

(D) liver failure is a possible sequela

(E) possible sequelae include hypergonadotropic hypogonadism in females

10.
The diagnosis of galactosemia is confirmed. You check the newborn screen results from the patient and find they were reported as normal. What are the possible explanations for why the newborn screen did not detect the galactosemia?

(A) the state where the child was born does not screen for galactosemia

(B) the child was placed on lactose-free milk (Isomil) immediately after birth

(C) the child had the newborn screen sent before receiving any formula, and the requested repeat testing was never performed

(D) all of the above

(E) none of the above

11.
Results of the laboratory screening of the child in case 83 show sodium 139 mEq/L, potassium 4.5 mEq/L, chloride 107 mEq/L, bicarbonate 7 mEq/ L, glucose 32 mg/dL, urine and serum ketones markedly positive, lactate of 7.2 mEq/L, ammonia level of 550 μmol/L, white blood cell (WBC) of 4.2, and platelet count of 75,000. The most likely diagnosis would be

(A) fatty acid oxidation defect

(B) glycogen storage disorder

(C) organic acidemia

(D) urea cycle defect

(E) none of the above

12.
Which of the following would be suspicious of a urea cycle defect?

(A) synthetic liver dysfunction with normal liver transaminases

(B) vomiting, lethargy, and tachypnea

(C) respiratory alkalosis, with an ammonia level of 1500 μmol/L

(D) hepatosplenomegaly, hypercholesterolemia, and hypoglycemia

(E) no clinical features differentiate organic acidemias from urea cycle defects

13.
If a urea cycle defect is suspected, appropriate treatments would include all of the following except

(A) removal of protein source

(B) IV glucose

(C) carnitine supplementation

(D) hemodialysis

(E) suspicion and possible treatment for cerebral edema

14.
Jaundice and liver dysfunction may be the presenting symptoms of which of the following inherited metabolic disorders?

(A) α
₁
-antitrypsin deficiency

(B) galactosemia

(C) neonatal hemochromatosis

(D) tyrosinemia

(E) all of the above

15.
Which of the following is not true regarding phenylketonuria (PKU)?

(A) PKU is an autosomal dominant disorder.

(B) PKU is a disorder of phenylalanine metabolism.

(C) untreated PKU leads to severe mental retardation (IQ 50) and seizures

(D) PKU is not easily recognized in a newborn infant

(E) mental retardation because PKU is rare because of newborn screening

16.
The newborn screening test (NBS) is positive for PKU in a premature baby born at 30 weeks of gestation who had multiple complications and was on total parenteral nutrition (TPN) at the time of the NBS. What is the most likely explanation?

(A) the child has PKU

(B) the child is a carrier for PKU

(C) the positive NBS is related to prematurity. The child probably does not have PKU and no further testing is indicated

(D) the positive NBS is related to prematurity. The child probably does not have PKU but repeat or confirmatory testing is indicated

(E) none of the above

17.
The treatment of PKU is characterized by

(A) restriction of dietary phenylalanine

(B) avoidance of fruits and vegetables that have high phenylalanine content

(C) careful monitoring of phenylalanine and tyrosine metabolism

(D) use of phenylalanine-free formulas but only during the first year of life

(E) A and C

18.
Which of the following is/are true regarding the long-term management of PKU?

(A) dietary restriction of phenylalanine may be discontinued after 8 years of age

(B) there is no further loss of IQ in untreated PKU after 6-10 years of age

(C) the outcome of pregnancy in untreated mothers with PKU leads to severe mental retardation, microcephaly, and birth defects in offspring

(D) dietary treatment during pregnancy eliminates the risks associated with maternal PKU

(E) all of the above

ANSWERS

1.
(E)
The clinical features of hypoglycemia include irritability, pallor, cyanosis, tachycardia, tremors, lethargy, apnea, seizures, diaphoresis, anxiety, headache, tachypnea, weakness, confusion, stupor, ataxia, and coma. When a patient presents with these features, a glucose determination by an oxidase reagent strip is indicated while the child is being stabilized and other investigations (such as the other options listed) are being considered and organized.

2.
(B)
Determining the underlying etiology of the hypoglycemia is of utmost importance but should not interfere with the primary goal of treatment with glucose. Prolonged exposure to hypoglycemia may result in irreversible brain damage and eventual death. Patients with symptoms and a glucose concentration less than 45 mg/dL and/or a glucose concentration of 25-35 mg/dL irrespective of symptoms require treatment. IV glucose is the first line of therapy. Glucose is administered in a dose of 0.5 g/kg. Dextrose 25% at a dose 2-4 mL/kg is also appropriate. In neonates and preterm infants, dextrose 10% at a dose of 5-10 mL/kg is used to avoid sudden hyperosmolarity. In older children and adolescents, dextrose 50% at a dose of 1-2 mL/kg is used. Patients with mild hypoglycemia who are capable of eating or drinking are treated with orange juice or some other age-appropriate source of oral glucose.

3.
(E)
The differential diagnosis of hypoglycemia includes metabolic diseases, endocrine disorders, poisoning, liver disease, and systemic disorders. It is often difficult to obtain all of the laboratory data needed in the diagnostic approach to hypoglycemia, but the initial laboratory data are crucial in refining the diagnostic possibilities. The endocrine causes of hypoglycemia can be determined by the tests mentioned and are maximally useful when obtained at the time of the hypoglycemia. The metabolic diagnosis leading to hypoglycemia can be categorized based on hepatomegaly, presence or absence of ketones, and studies that reflect fat, protein, and carbohydrate metabolism. The metabolic laboratory tests are still useful even if obtained within the first few hours after the hypoglycemia. They can be misleading, however, if done days after recovery; in some diseases, the metabolic abnormalities will normalize with time.