Alpha thallasemia clarification

[ThermParticipant]

In the hematology section on alpha thal, 3 missing alpha chains should be hgb H and 4 missing alpha is 4.

[ashishMember]

Hey therm,

Thanks for the question. It’s a confusing and low-yield topic so please don’t spend too much time on it. You’re partially correct so thank you for bringing my attention to it. The updated version is below:

ALPHA THALASSEMIA

Alpha thalassemia refers to a mutation in an alpha chain allele. Because of the defect, other types of hemoglobin persist. You will find elevated levels of fetal hemoglobin (hgb F) as well as elevated levels of “minor adult hemoglobin” (hgb A2). There will only be low levels of A1. Patients with alpha thalassemia do fairly well and only have a mild microcytosis.

PEARL: The only thing you probably need to know for the exam is that alpha thalassemia can cause a microcytic anemia and cannot be diagnosed by hemoglobin electrophoresis.

MNEMONIC: Be familiar with, but do not memorize this. It’s doubtful that you will be asked to name the types of alpha thalassemia on the exam, but if you are, try this – “silent… trait (or minor)… barts… DEAD!” If one allele is mutated the patient is said to be a “silent carrier”, if 2 = trait or minor, 3 = Hemoglobin H disease (or Barts) and 4 = Major (or hydrops fetalis)! Four defective alleles are not compatible with life since ALL types of hemoglobin have alpha chains. Hgb A1 = alpha-beta, Hgb S = alpha-beta (but with a defective beta due to glu-val), Hgb A2 = alpha-delta and Hgb F = alpha-gamma.

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