Pediatric Examination and Board Review (150 page)

16.
(B)
The osmotic fragility test is the most specific test for the diagnosis of hereditary spherocytosis. Red blood cells are incubated in the presence of varying degrees of hypotonic solutions, and the red blood cell lysis is measured. Spherocytes, as a result of their decreased surface area, will be more susceptible to hypotonic lysis compared with normal red blood cells. The Coombs test detects the presence of antibodies in cases of autoimmune hemolytic anemia, which can be associated with spherocytes visualized on a peripheral smear but will be negative in cases of hereditary spherocytosis. Platelet aggregation studies and hemoglobin electrophoresis are not useful in the diagnosis of spherocytosis.

17.
(B)
Splenectomy should be an option for any patient with hereditary spherocytosis who requires frequent transfusions, has severe symptoms of anemia such as cardiac dysfunction or poor growth, has severe splenomegaly with significantly increased risk of rupture, or has persistent symptoms of hypersplenism such as leukopenia or thrombocytopenia. Splenectomy usually results in a persistently elevated baseline hemoglobin. Patients undergoing splenectomy should receive immunizations against
H influenzae
and
S pneumoniae
if possible before surgery, and they should be started on penicillin prophylaxis as soon as possible after splenectomy. Furthermore, splenectomy should be avoided if possible until patients are older than 5 years to reduce the incidence of severe bacterial infections that can occur in younger children. Exchange transfusions are not indicated for the treatment of spherocytosis, and steroids have no effect. Spectrin replacement is not yet a viable treatment option (see
Figure 87-3
).

18.
(C)
S pneumoniae
,
H influenzae
type b, and
E coli
can all be encapsulated organisms, and patients with either splenic hypofunction or those undergoing splenectomy are at increased risk for infections from these and other encapsulated organisms.
M pneumoniae
is not an encapsulated organism, and splenectomized patients are not at a higher risk of mycoplasma infections. Patients who need a splenectomy should receive
H influenzae
and pneumococcal vaccines before the splenectomy, and then they should receive penicillin prophylaxis postsplenectomy to reduce the incidence of bacteremia and sepsis from encapsulated organisms.

FIGURE 87-3.
Sickle cell anemia, dactylitis. Note the swelling of the right thumb and first and second fingers. There is a high frequency of dactylitis in children with sickle cell anemia between the time of birth and four years of age with a mode at about one year. This swelling is associated with limited vascular necrosis of marrow and may affect the hands and feet. (Reproduced, with permission, from Lichtman MA, Beutler E, Kipps TJ, et al. Williams Hematology, 8th ed. New York: McGraw-Hill; 2006: Fig. 48-10.)

S
UGGESTED
R
EADING

Cashore WJ. Neonatal hyperbilirubinemia. In: McMillan JA, DeAngelis CD, Feigin RD, et al, eds.
Oski’s Pediatrics
:
Principles and Practice.
4th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2006.

Committee on Infectious Diseases, American Academy of Pediatrics. Immunization in special circumstances. In: Pickering LK, Baker CJ, Kimberlin DW, Long SS, eds.
Red Book 2009 Report of the Committee on Infectious Diseases.
28th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2009.

Gallagher PG, Jarolin P. Red cell membrane disorders. In: Hoffman R, Benz EJ, Shattil SJ, et al, eds.
Hematology
:
Basic Principles and Practice.
5th ed. Philadelphia, PA: Churchill Livingstone; 2008.

Prchal JT, Gregg XT. Red cell enzymopathies. In: Hoffman R, Benz EJ, Shattil SJ, et al, eds.
Hematology
:
Basic Principles and Practice.
5th ed. Philadelphia, PA: Churchill Livingstone; 2008.

Tabbara IA. Hemolytic anemias: diagnosis and management.
Med Clin North Am.
1992;76(3):649-668.

Watchko JF. Identification of neonates at risk for hazardous hyperbilirubinemia: emerging clinical insights.
Pediatr Clin North Am
. 2009;56:671-687.

CASE 88: AN 18-MONTH-OLD GIRL WITH ANEMIA

An 18-month-old Hispanic girl is brought to your office for routine evaluation. A screening hemoglobin level was noted to be 4.6 g/dL. The child does appear pale and has a “cranky” disposition, according to the parents. On further history, the child’s parents inform you that her diet consists of approximately 36 ounces of cow’s milk per day. There is no prior history of anemia and no history of pica, trauma, or recent blood loss. The child is the product of a full-term, uncomplicated pregnancy and has been doing well, with no other medical problems and normal growth and development to date. There is no family history of blood disorders.

Her physical examination is notable for mild pallor and a 2/6 systolic ejection murmur at the left sternal border.

SELECT THE ONE BEST ANSWER

1.
The most likely diagnosis for this child is

(A) acute lymphoblastic leukemia

(B) iron deficiency anemia

(C) lead poisoning

(D) anemia of chronic disease

(E) G6PD

2.
The most useful diagnostic test at this point would be

(A) complete blood count with smear

(B) serum ferritin level

(C) hemoglobin electrophoresis

(D) direct and indirect Coombs test

(E) G6PD screen

3.
The differential diagnosis of a child with microcytic anemia includes all of the following except

(A) lead intoxication

(B) folate deficiency

(C) iron deficiency

(D) anemia of chronic disease

(E) thalassemia

4.
Most of the body’s iron is located in the

(A) erythrocytes

(B) splenic histiocytes

(C) cardiac myocytes

(D) hepatocytes

(E) skeletal myocytes

5.
Which of the following compounds does
not
inhibit iron absorption from the gastrointestinal (GI) tract?

(A) ascorbic acid

(B) phytates

(C) phosphates

(D) sodium bicarbonate

(E) antacids

6.
Which of the following is the least likely cause of iron deficiency in adolescents?

(A) menorrhagia

(B) pregnancy

(C) pubertal growth acceleration

(D) sedentary lifestyle

(E) diet

7.
Which of the following is not a complication of iron deficiency anemia?

(A) geophagia (compulsive dirt eating)

(B) cognitive delay

(C) hypertrophic cardiomyopathy

(D) short stature

(E) rapid or irregular heartbeat

8.
Which of the following is a laboratory finding associated with iron deficiency?

(A) increased serum TIBC (total iron-binding capacity)

(B) increased serum ferritin

(C) increased red blood cell mean corpuscular volume (MCV)

(D) increased serum iron

(E) decreased red blood cell red distribution width (RDW)

9.
Treatment options for children with iron deficiency anemia include all of the following except

(A) red blood cell transfusion

(B) oral ferrous sulfate

(C) intravenous iron dextran

(D) oral folic acid

(E) iron-rich diet

10.
Beta-thalassemia is found most commonly among which of the following ethnic groups?

(A) Southeast Asian

(B) northern European

(C) Ashkenazi Jewish

(D) American Indian

(E) Japanese