From GT:
"A 17-year-old male who recently emigrated, with his family, from Cambodia presents in your clinic for continued management of his anemia. His peripheral smear is shown. A medical report indicates the presence of hemoglobin α2δ2. Which is the likely diagnosis?
A. Iron deficiency anemia
B. One deletion of the α-globin gene
C. Two deletions of the β-globin gene
D. Two deletions of the α-globin gene
E. Three deletions of the β-globin gene
Answer Explanation
The correct answer is D.
This patient has a hypochromic, microcytic anemia. Classically, the presence of HbA2 (α2δ2) suggests β-thalassemia minor. However, this is not one of the answer choices.
The learning point is that HbA2 is present in mild alpha-thalassemia – there's not enough of an alpha-chain deficiency to prevent the formation of HbA2. Hence, the correct answer is 2 deletions of the α-globin gene.
One α-globin deletion would not cause a microcytic anemia. Two deletions of the β-globin gene would cause beta-thalassemia major."
The blood smear just showed typical target cells.
I understand the "learning point" that two alpha deletions could still yield the possibility for increased HbA2 and that him being Asian makes alpha, vs beta, more likely. I'm not questioning that.
I would just think HbA2 levels would, overall, be highest in Cooley's because there's no other way to compensate than to produce HbA2 and HbF (and epsilon and other less significant types), whereas in alpha thalassaemia trait (two deletions), although HbA2 is found, it wouldn't be nearly as abundant because HbA1 is still produced.
The only thing I can think of is that this question-writer was merely trying to emphasize the point that he's Asian and nothing else. Therefore, beta shouldn't even be considered, and that's the only alpha choice that's relevant.
