41 Sickle Cell Trait (Hemoglobin AS)
Michelle To and Valentin Villatoro
Cause(s):
β globin chain amino acid substitution in the 6th position from glutamic acid (Glu) to valine (Val). Only one β globin genes is affected.1,2
Inheritance:
Heterozygous state where one normal β globin gene and one affected β globin gene are inherited.3
Clinical Findings:1-3
Due to the presence of Hb A and reduced concentration of HB S, polymerization of Hb S and sickling of red blood cells does not normally occur. As a result, condition is mostly benign and asymptomatic.
Sickling can still occur under extremely low hypoxic conditions.
Laboratory Features:1-3
|
CBC: All parameters (Even Hb) are normal |
PBS: Absence of sickle cells PBS appears normal (may see a slight increase in target cells) |
BM: N/A |
|
Hemoglobin Electrophoresis: Hb S: 35-45% Hb A: 50-65% Hb A2: Normal Hb F: Normal Hb A:Hb S is ~60:40 |
Other Tests: Solubility Screen: Positive Metasulfite Sickling Test: Positive HPLC Hemoglobin Electrophoresis |
References:
1. Laudicina RJ. Hemoglobinopathies: qualitative defects. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p.231–50.
2. Harmening DM, Yang D, Zeringer H. Hemolytic anemias: extracorpuscular defects. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 250-79).
3. Randolph TR. Hemoglobinopathies (structural defects in hemoglobin). In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 426-453.
