Master the board step 3

Master the Boards: USMLE Step 3
Diagnostic Testing
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Best initial screening: Blood lead testing at 12 and 24 months in high-risk
children. Blood lead level (BLL) ≤ 5 mcg/dL is acceptable.
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Labs: Microcytic, hypochromic anemia, increased free erythrocyte porphyrins
(FEP), and basophilic stippling
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X-rays of long bones (dense lead lines)
Treatment
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Refer to department of health when blood lead level > 15 mcg/dL.
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Begin chelation when blood lead level > 45 mcg/dL.
Hemoglobin (Hb) Disorders
A 6-month-old, previously well African-American infant presents to the pediatrician
with painful swollen hands and swollen feet. What are the most common
causes of mortality in pediatric cases with sickle cell disease?
Answer:
• Infection (autosplenectomy by age 5) leads to increased susceptibility to infection,
particularly with encapsulated bacteria (S. pneumococcus, H. influenzae, N. meningitidis).
• Acute chest syndrome (this and sepsis are most common causes of mortality).
• Acute splenic sequestration (peak incidence from 6 months to 3 years of age).
Diagnostic Testing
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Best diagnostic test: Hb electrophoresis (also used in newborn screening)
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Prenatal diagnosis for parents with trait:
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Chorionic villus sampling at 10–12 weeks gestation; or
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Amniocentesis at 14–18 weeks
Treatment
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Transfuse in the following situations:
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Symptomatic anemia (shortness of breath or chest pain)
Recurrent painful crises
are not an indication for
transfusion.
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Exchange transfusion in the following situations:
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Life-threatening complications (stroke, acute chest syndrome, splenic crisis)
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Before high-risk surgery
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Give aggressive antibiotic therapy for infections.
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Hydroxyurea: Increases HbF levels. Reduces recurrent painful crises and
number of transfusions. Does not reduce risk of stroke. Indicated in the following
situations:
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≥ 3 crises per year
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Symptomatic anemia
--
Life-threatening complications
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