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African American boy

2K views 4 replies 5 participants last post by  maqsteps 
#1 ·
A 4-year-old previously well African American boy is brought to the office by his aunt. She reports that he developed pallor, dark urine, and jaundice over the past few days. He stays with her, has not traveled, and has not been exposed to a jaundiced person, but he is taking trimethoprimsulfamethoxazole for otitis media. The CBC in the office shows a low hemoglobin and hematocrit, while his 'stat' serum electrolytes, BUN, and chemistries are remarkable only for an elevation of his bilirubin levels. His aunt seems to recall his 8-year-old brother having had an 'allergic reaction' to aspirin, which also caused a short-lived period of anemia and jaundice. Which of the following is the most likely cause of this patient's symptoms?

  1. Hepatitis B
  2. Hepatitis A
  3. Hemolytic-uremic syndrome
  4. Gilbert syndrome
  5. Glucose-6-phosphate dehydrogenase deficiency
 
#5 ·
E

The answer is e, Glucose-6-phosphate dehydrogenase deficiency.

Synthesis of the red-cell enzyme glucose-6phosphate dehydrogenase (G6PD) is determined by genes on the X chromosome, and the pattern of inheritance is X-linked recessive. The enzyme found in most populations is termed G6PDB1. There are more than 380 deficient variants of the enzyme, affecting over 100 million people worldwide, among them G6PDA1, a mutant enzyme affecting about 13% of African American males and 2% of African American females. The disease occurs, though less commonly, in other ethnic groups, including Middle Eastern, African, and Asian groups. Deficiency of G6PD compromises the generation of reduced glutathione, and upon exposure to oxidant agents such as sulfa drugs, antimalarials, nitrofurans, naphthalene mothballs, or infection, a hemolytic episode usually occurs. The degree of hemolysis depends on the nature of the oxidant and severity of the enzyme deficiency. In African Americans, the older, more G6PD-deficient cells are destroyed, but since young cells have sufficient enzyme to prevent further red-cell destruction even if the inciting factor is still present, the hemolytic crisis is usually self-limited. Blood transfusion may be unnecessary. In African Americans, premature testing for the enzyme immediately after a hemolytic episode can lead to a false-negative result, since the newly produced red cells in the circulation have a higher G6PD enzyme activity. The older red cells containing Heinz bodies (insoluble precipitates resulting from oxidation), the 'bite cells' (red cells after the removal of the Heinz bodies), and cell fragments are removed from the circulation within 3 to 4 days. In the severe Mediterranean type, young as well as old red cells are enzyme-deficient. Recovery is signaled by the appearance of reticulocytes and a rise in hemoglobin.

Hepatitis A or B often will occur after an exposure, and usually does not cause anemia as a presenting sign. Gilbert syndrome presents with episodes of jaundice, but not anemia. Hemolytic-uremic syndrome must be considered in a clinical situation similar to that presented, but the absence of uremia makes the diagnosis less likely.
 
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