Clinical Pathology: General Principles, Hematology & Coagulation

394) A 23-year-old African American woman is seen by her obstetrician for a routine prenatal visit. A complete blood cell count (CBC) was performed and is shown in the table. Results of hemoglobin electrophoresis are shown in the figures. The sickle solubility test result was negative. Which one of the following is the best diagnosis based on these results?
Patient Reference Range Units
WBC 5.8 3.04–9.06 ×109/L
RBC 3.7 4.3–5.6 ×1012/L
Hemoglobin 10.9 13.3–16.2 g/dL
Hematocrit 30.6 38.8–46.4 %
MCV 81.0 79.0–93.3 fL
MCH 28.8 26.7–31.9 pg
MCHC 35.6 32.3–35.9 g/dL
RDW 13.3 <14 %
PLT 271 165–415 ×109/L

• Hemoglobin C is a β-chain hemoglobin variant that results from a mutation in the β-globin gene (β6Glu->Lys).

• Glutamate is a negatively charged amino acid and lysine is positively charged; which results in a +2 net gain of charge. Therefore, it migrates slower than hemoglobin A and hemoglobin S on alkaline electrophoresis.

• Hemoglobin C trait (hemoglobin A/hemoglobin C; ββC) is a clinically asymptomatic hemoglobinopathy.

• It is important to identify the presence of hemoglobin C for genetic counseling and prenatal testing. When a child inherits hemoglobin C from one parent and hemoglobin S (βS) from the other parent, the child will have the clinically significant sickling disorder hemoglobin SC disease.

• Hematologically, the hemoglobin is usually normal in hemoglobin C trait. The mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) can be normal or slightly below the reference range because of red cell dehydration. The peripheral blood smear is normal, or it can show hypochromia and microcytosis and/or target cells.

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