A 32-year-old man of Mediterranean descent is brought to the physician because of a 2-day history of fatigue and shortness of breath. He recently had a urinary tract infection treated with trimethoprimsulfamethoxazole. His pulse is 100/minute. Physical examination shows pallor and scleral icterus. Laboratory studies show a decreased erythrocyte count and an increased serum bilirubin concentration that is mainly indirect. This patient's anemia is most likely due to failure of which of the following?

Question

Quizplus · Accepted Answer

The patient likely has G6PD deficiency, common in individuals of Mediterranean descent, leading to hemolytic anemia due to oxidative stress from drugs like trimethoprim-sulfamethoxazole. This condition impairs erythrocyte protection against membrane oxidation.  Erythrocytes require a continuous source for NADPH to ensure that oxidized glutathione can be reduced by the glutathione peroxidase system. Glutathione is oxidized when it scavenges reactive oxygen species and by reducing oxidized membrane lipids. Administration of oxidizing drugs such as those of the sulfa class can lead to weakening of erythrocyte plasma membranes due to rapid depletion of reduced glutathione levels and inadequate NADPH-dependent reduction of the oxidized form.

A 32-Year-Old Man of Mediterranean Descent Is Brought to the Physician