Questions 1 to 5 The Patient: A 10-year old black male child named Michael Jones

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Questions 1 to 5

The Patient: A 10-year old black male child named Michael Jones was admitted to the hospital because he was experiencing severe chest pain. He had been hospitalized on several previous occasions for vaso-occlusive episodes that caused him to experience severe pain that could not be managed with non-prescription drugs such as ibuprofen. He was slightly jaundiced, short of breath and easily tired, and feverish. A chest x-ray was taken and was abnormal. An arterial blood sample showed a P_oz value of 6 kPa (normal is 10 - 13 kPa). As Michael's blood sample was waiting for processing a lab technician noticed that the red blood cells at the bottom of the tube had a strange, elongated shape. When the technician mixed the blood the red blood cells returned to their normal shape. A portion of Michael's blood was smeared onto a microscope slide and the following picture was obtained: Furthermore, the cells were lysed, run on a non-denaturing (ie, simple) electrophoresis gel to separate the proteins, and stained for hemoglobin. Lanes 1 - 3 are standards, lane 4 is from Michael's blood, and lane 5 is a reference sample of "normal" blood. The following gel was obtained: What is the most likely diagnosis for Michael? A. Carbon monoxide poisoning B. Dietary anemia (low intake of iron) C. Pernicious anemia (due to a vitamin B12 deficiency) D. Sickle cell anemia Why does the hemoglobin from Michael's blood not run as for on the electrophoresis gel as the normal sample? A. Sickle hemoglobin (HbS) is a longer protein than normal hemoglobin (HbA) so does not travel as for in the gel. B. HbS aggregate together and since this was a non-denaturing gel there are multiple copies of HbS trying to run together through the gel. C. HbS has been cleaved as compared to HbA so runs differently. D. HbS has a different overall net charge than HbA, which causes it to run differently through the gel. What is the best explanation for the observation of abnormally shaped red blood cells at the bottom of Michael's blood sample that appear to correct themselves when the sample was mixed? A. The sickle shape is more pronounced when the hemoglobin is in the T state, which would be more likely at the bottom of the tube due to lower oxygen availability. B. The sickle shape is more pronounced when the hemoglobin is in the R state, which would be more likely or the bottom of the tube due to lower oxygen availability. C. The sickle cells are more dense than normal shaped cells so they settle to the bottom of the tube. D. The lab technician was seeing things, there were no differences in the cells at the bottom of the tube. In the gel, which lane would took the most similar to what would be obtained if Michael's parents had their blood sampled? A. Lane 1 B. Lane 2 C. Lane 3 The doctors treated Michael in part by administering 100% oxygen (normal air is 20% oxygen), which alleviated some of his symptoms. Why would 100% oxygen be an effective treatment for Michael? A. HbS can only bind 1 oxygen per Hb molecule so more oxygen is repaired to allow for effective transport to the rest of the body. B. HbS has a lower affinity for oxygen so more oxygen is required to get HbS fully saturated with oxygen. C. High oxygen will activate the release of BPG to result in more oxygen being delivered to the tissues. D. High oxygen will cause other oxygen carriers to be activated. A medical student shadowing the case speaks up about a new drug treatment for sickle cell anemia that they had read about. The drug is hydroxyurea, and is thought to function by stimulating the affected person's synthesis of fetal hemoglobin (HbF). HbF is composed of two alpha chains and two gamma chains and is expressed in a developing fetus beginning at the third month of gestation and continues up through birth when the expression of the gamma chain, and therefore HbF declines, in a clinical study, patients who

Explanation / Answer

1-

The correct answer is option D- sickle-shaped anemia.

2- Sickle-shaped anemia is caused due to a point mutation which changes the glutamic acid to valine amino acid in the Beta chain of the hemoglobin. Glutamic acid gives the hemoglobin net negative charge and since valine is hydrophobic amino acid it will not give any net charge to the hemoglobin.

So the correct answer is option D.

3- Sickle-shaped RBCs are seen when the Hemoglobin is in T-state. In T-state Hemoglobin, molecule binds to other hemoglobin molecules which are in S-state thus gives the RBCs sickle-shaped.

So the correct answer is option A.

4- There might be two possibilities.

Either both the parents have the two copies of HbS gene or both of them have one copy of normal Hb and one copy of HbS.

So the correct answer might be lane 1 or lane 2.

5- If we look at the oxygen dissociation curve of hemoglobin we will find that sickle shaped hemoglobin shift the curve towards the right-hand side which means that we need more oxygen to reach the P50 of the oxygen.

So the correct answer is option is B

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