Question
A 7-year-old patient presents to your office accompanied by his parents. He has been hospitalized multiple times for painful episodes in his hands and feet over the last several years. He has no known medical problems and takes no medications except for acetaminophen for pain control. You suspect that he has a valine for glutamic acid substitution at position 6 of the 13-globin chain of the hemoglobin molecule. This patient’s hemoglobin would most likely aggregate upon:
| A. |
β-chain folding |
| B. |
Interaction with HbF |
| C. |
Proton release |
| D. |
Oxygen unloading |
Show Answer
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Correct Answer � D Explanation |
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Ans. D. Oxygen unloading
Explanation:Hemoglobin S (HbS) aggregates in the deoxygenated state. HbS polymers form fibrous strands that reduce red blood cell membrane flexibility and promote sickling. Sickling occurs under all conditions associated with anoxia including low pH and high 2,3-DPG. These inflexible erythrocytes predispose to microvascular occlusion and microinfarction.