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420 SectIon III Hematology and oncology ` hematology and oncology—Pathology Hematology and oncology ` hematology and oncology—Pathology
Macrocytic anemias MCV > 100 fL.
deScRIPtIon FIndIngS
Megaloblastic anemia Impaired DNA synthesis maturation of RBC macrocytosis, hypersegmented neutrophils
nucleus of precursor cells in bone marrow (arrow in A ), glossitis.
A
delayed relative to maturation of cytoplasm.
Causes: vitamin B deficiency, folate deficiency,
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medications (eg, hydroxyurea, phenytoin,
methotrexate, sulfa drugs).
Folate deficiency Causes: malnutrition (eg, alcoholics), homocysteine, normal methylmalonic acid.
malabsorption, drugs (eg, methotrexate, No neurologic symptoms (vs B deficiency).
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trimethoprim, phenytoin), requirement (eg,
hemolytic anemia, pregnancy).
Vitamin B Causes: pernicious anemia, malabsorption homocysteine, methylmalonic acid.
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(cobalamin) (eg, Crohn disease), pancreatic insufficiency, Neurologic symptoms: reversible dementia,
deficiency gastrectomy, insufficient intake (eg, veganism), subacute combined degeneration (due to
Diphyllobothrium latum (fish tapeworm). involvement of B in fatty acid pathways and
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myelin synthesis): spinocerebellar tract, lateral
corticospinal tract, dorsal column dysfunction.
Folate supplementation in vitamin B
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deficiency can correct the anemia, but worsens
neurologic symptoms.
Historically diagnosed with the Schilling test,
a test that determines if the cause is dietary
insufficiency vs malabsorption.
Anemia 2° to insufficient intake may take several
years to develop due to liver’s ability to store B
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(as opposed to folate deficiency).
Orotic aciduria Inability to convert orotic acid to UMP Orotic acid in urine.
(de novo pyrimidine synthesis pathway) Treatment: uridine monophosphate or uridine
because of defect in UMP synthase. triacetate to bypass mutated enzyme.
Autosomal recessive. Presents in children as
failure to thrive, developmental delay, and
megaloblastic anemia refractory to folate
and B . No hyperammonemia (vs ornithine
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transcarbamylase deficiency— orotic acid
with hyperammonemia).
Nonmegaloblastic Macrocytic anemia in which DNA synthesis is RBC macrocytosis without hypersegmented
anemia normal. neutrophils.
Causes: alcoholism, liver disease.
Diamond-Blackfan A congenital form of pure red cell aplasia. % HbF (but total Hb).
anemia Rapid-onset anemia within 1st year of life due Short stature, craniofacial abnormalities, and
to intrinsic defect in erythroid progenitor cells. upper extremity malformations (triphalangeal
thumbs) in up to 50% of cases.
FAS1_2019_10-HemaOncol.indd 420 11/7/19 5:05 PM
