Pediatric Examination and Board Review (153 page)

His white blood cell count is 16,500/μL, with a hemoglobin of 6.5g/dL and a platelet count of 426,000/μL. His differential has 65% neutrophils, 25% lymphocytes, 8% monocytes, and 2% eosinophils. His reticulocyte count is 18.6%. A chest radiograph reveals a small fluffy infiltrate in the right lower lobe of the lung.

SELECT THE ONE BEST ANSWER

1.
At this time, the patient most likely has which of the following complications of sickle cell disease?

(A) splenic sequestration

(B) aplastic crisis

(C) priapism

(D) acute chest syndrome

(E) splenic infarction

2.
The most common symptoms associated with acute chest syndrome in pediatric patients with sickle cell disease include all of the following except

(A) hemoptysis

(B) temperature higher than 101.3°F (38.5°C)

(C) oxygen saturation less than 90%

(D) chest pain

(E) bone pain

3.
The management of acute chest syndrome should include all of the following except

(A) opioids for pain control

(B) broad-spectrum antibiotics

(C) aerosolized nitrous oxide

(D) incentive spirometry

(E) acetaminophen for fever

4.
Which of the following antibiotics is the best initial choice in the management of a patient with sickle cell disease and fever?

(A) ceftriaxone

(B) clindamycin

(C) vancomycin

(D) metronidazole

(E) penicillin

5.
Which of the following is not a side effect of the opioids used for pain management in children with sickle cell disease?

(A) constipation

(B) nausea

(C) pruritus

(D) hematuria

(E) fatigue

6.
Acute chest syndrome is most common in patients with which of the following hemoglobin genotypes?

(A) AS

(B) SS

(C) SC

(D) beta-thalassemia

(E) hemoglobin E disease

7.
Recurrent acute chest syndrome is associated with all of the following complications except

(A) chronic hypoxia

(B) pulmonary hypertension

(C) emphysema

(D) cor pulmonale

(E) anoxic brain injury

8.
Which of the following is the most likely result of neonatal hemoglobin electrophoresis for patients with sickle cell trait?

(A) FS

(B) FSC

(C) FA

(D) FAS

(E) FC

9.
Which of the following is the approximate hemoglobin S gene carrier frequency in the U.S. African American population?

(A) 4%

(B) 8%

(C) 16%

(D) 32%

(E) 48%

10.
Which of the following findings on the peripheral blood smear is a feature of decreased splenic function in patients with sickle cell disease?

(A) Auer bodies

(B) basophilic stippling

(C) Howell-Jolly bodies

(D) polychromasia

(E) blasts

11.
Renal complications of patients with sickle cell anemia include all of the following except

(A) hyposthenuria

(B) hematuria

(C) proteinuria

(D) glucosuria

(E) renal failure

12.
Gallstones found in patients with sickle cell anemia are composed primarily of which of the following compounds?

(A) calcium oxalate

(B) calcium bilirubinate

(C) calcium carbonate

(D) xanthine oxide

(E) cholesterol

13.
Acute hemiparesis in patients with sickle cell disease is best managed by which of the following?

(A) red blood cell transfusion

(B) red blood cell exchange transfusion

(C) nonsteroidal anti-inflammatory agents

(D) hyperbaric oxygen

(E) heparin

14.
All of the following are neurologic complications of strokes in pediatric patients with sickle cell disease except

(A) recurrent stroke

(B) cognitive delay

(C) optic neuritis

(D) seizure disorder

(E) moyamoya

15.
Which of the following has been shown to be
most
effective in preventing recurrence of strokes in patients with sickle cell disease?

(A) aspirin

(B) low molecular weight heparin

(C) folic acid

(D) regular red blood cell transfusions

(E) heparin

16.
Aplastic crises in patients with sickle cell disease are
most
commonly associated with which of the following infections?

(A) Epstein-Barr virus

(B) adenovirus

(C)
S pneumoniae
(D) parvovirus B19

(E) cytomegalovirus

17.
Which of the following complications of sickle cell disease is most likely to occur during infancy?

(A) priapism

(B) transient ischemic attack

(C) acute chest syndrome

(D) dactylitis

(E) stroke

18.
Which of the following antibiotics is most effective for prophylaxis against
S pneumoniae
in patients with sickle cell disease?

(A) trimethoprim-sulfamethoxazole

(B) penicillin

(C) rifampin

(D) fluconazole

(E) azithromycin

19.
Which of the following statements about hydroxyurea treatment in patients with sickle cell disease is false?

(A) beneficial effects of hydroxyurea can begin in the first few weeks after commencing therapy

(B) hydroxyurea can decrease elevated transcranial Doppler velocities

(C) hydroxyurea induces erythroid regeneration and the premature commitment of erythroid precursors, with resulting increased production of hemoglobin F

(D) hydroxyurea treatment has been shown to reduce vaso-occlusive pain crises in patients with sickle cell disease

(E) the dose of hydroxyurea is titrated according to the patient’s renal function.

ANSWERS

1.
(D)
Sickle cell disease is characterized by a mutation in the hemoglobin beta chain, where a valine is substituted for a glutamic acid at the β6 position. This amino acid substitution predisposes the hemoglobin molecule to polymerization, particularly under hypoxic or acidic conditions, with hemoglobin polymerization resulting in “sickling” of the red blood cell. Symptoms of sickle cell disease can occur with hemoglobin genotypes including homozygous hemoglobin SS and combinations of hemoglobin S with other mutant beta-globin chains, such as hemoglobin SC, Sβ
⁰
thalassemia, or Sβ+ thalassemia. The disease severity varies to some degree with the genotype because patients with SS and Sβ
⁰
genotypes tend toward more severe disease. Red blood cell sickling and the resulting microvascular obstruction is the cause of the wide range of complications associated with sickle cell disease.

In a patient with sickle cell disease of any genotype, the combination of respiratory symptoms, fever, chest pain, and an infiltrate on chest radiograph after an episode of vaso-occlusive pain are all consistent with the diagnosis of acute chest syndrome. Acute chest syndrome occurs at least once in up to 50% of patients with sickle cell disease. The etiology of acute chest syndrome in patients with sickle cell disease is unclear but may include components of both pulmonary infection and infarction in addition to fat embolism from infarcted bone marrow. Therefore, any combination of the symptoms just listed should be treated as acute chest syndrome. Patients who have had prior episodes of acute chest syndrome are more likely to have recurrent episodes.

2.
(A)
The most common symptoms in pediatric acute chest syndrome are fever and cough, with approximately 70% also having some degree of hypoxia. Chest pain, dyspnea, and wheezing can be seen less commonly. Up to 60% of patients, however, will have a normal pulmonary examination. Although hemoptysis occurs frequently in adult sickle cell patients with acute chest syndrome, it is rare in pediatric sickle cell patients. Other associated findings with acute chest syndrome include a drop in hemoglobin and an elevation in the baseline white blood cell count. Acute chest syndrome, if not appropriately treated, can rapidly progress to respiratory insufficiency and acute respiratory distress syndrome (ARDS) and can be fatal.

3.
(C)
The management of acute chest syndrome requires multiple interventions. Pain control to prevent respiratory “splinting” is important because the inability to take deep breaths will lead to further lung collapse and worsening of the acute chest syndrome. However, oversedation with respiratory depression should also be avoided, and so the opioid dose in patients with acute chest syndrome must be carefully titrated. Intravenous hydration is also important because dehydration contributes to further intravascular sickling. Overhydration with potential pulmonary edema and worsening symptoms must also be avoided. Antibiotics to cover the possible infectious etiologies (which include
S pneumoniae
,
H influenzae
,
N meningitidis
,
Chlamydophila [Chlamydia] pneumoniae,
and
M pneumoniae
, as well as many other bacteria and viruses) are important in the management of acute chest syndrome. Incentive spirometry to maintain alveolar patency is also important, and bronchodilator therapy can be a useful adjunct as well. Intubation for severe respiratory distress may also be required. Nitrous oxide therapy is not recommended for the management of acute chest syndrome.

Red blood cell transfusions are the most effective therapy for acute chest syndrome. Patients with sickle cell disease generally have baseline hemoglobin values of 7-9 g/dL, and transfusions that raise the hemoglobin well above this range can lead to hyperviscosity and further sickle cell complications such as strokes. Those patients with baseline hemoglobin values higher than 10 g/dL should undergo exchange transfusion rather than simple transfusion to avoid hyperviscosity complications. The goal for blood transfusion or exchange transfusion should be to lower the percentage of sickled cells in the blood while avoiding further complications.