A 6-year-old African American male is brought to your office for a routine check-up. His mother remarks that he often seems uninterested in playing with his peers and appears to "run out of breath quickly." His medical records reveal that he has missed several pediatric vaccinations and has been hospitalized twice, once with a "chest infection" and once with abdominal pain. The patient mentions to you that occasionally his "bones hurt." Which of the following protein changes most likely accounts for this patient's condition?

Question

A 6-year-old African American male is brought to your office for a routine check-up.  His mother remarks that he often seems uninterested in playing with his peers and appears to "run out of breath quickly."  His medical records reveal that he has missed several pediatric vaccinations and has been hospitalized twice, once with a "chest infection" and once with abdominal pain.  The patient mentions to you that occasionally his "bones hurt."  Which of the following protein changes most likely accounts for this patient's condition?

Quizplus · Accepted Answer

This patient is exhibiting signs and symptoms of sickle cell anemia. Sickle cell anemia is a hemoglobinopathy that typically affects patients of African ancestry. A point mutation in the 6^th codon of the beta-globin gene, which causes the substitution of valine (hydrophobic) for glutamic acid (hydrophilic), is responsible. The incorporation of this abnormal beta-globin protein into hemoglobin results in the formation of hemoglobin S (HbS). HbS polymerizes at low oxygen tension, causing sickling and hemolysis of erythrocytes and resultant vascular occlusion. This patient's poor exercise tolerance and exertional dyspnea are due to anemia. His history of acute chest syndrome, abdominal pain, and bone pain are due to vaso-occlusive events in the lungs, spleen and bone, respectively. (Choice A) A phenylalanine deletion (ΔF508) is the most common cause of cystic fibrosis, the most common fatal genetic disease of Caucasians. (Choice E) Early termination of polypeptide synthesis (nonsense mutation) will produce a truncated protein. Educational Objective: Exertional dyspnea, pneumonia resulting in life-threatening acute chest syndrome, and recurrent abdominal and bone pain are clinical features of sickle cell anemia. Sickle cell anemia results from a point mutation that causes valine to substitute for glutamic acid in the sixth position of the b-globin chain of hemoglobin.

A 6-Year-Old African American Male Is Brought to Your Office