Which of the following is a typical finding in patients with Hb M?
a. Severe anemia requiring repeated blood transfusions
b. Elevated levels of ferrous iron (Fe2+) in the red cells
c. Presence of Heinz bodies on Wright-stained blood film
d. Elevated methemoglobin
ANS: D
Methemoglobin is elevated in Hb M. Affected persons may have 30% to 50% methemoglobin (Fe2+). The amino acid substitutions found in the various Hb Ms cause heme iron to autooxidize, forming methemoglobin. Heinz bodies may be present, but they are not visible with a Wright stain.
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