A 26-year-old man presents to the emergency department with fatigue and dark urine over the past day. He was recently diagnosed with cellulitis of his left leg, for which he was prescribed trimethoprim-sulfamethoxazole. He denies having nausea, vomiting, or diarrhea. He has no significant medical history and does not currently take any medications. His temperature is 98.6°F (37°C), blood pressure is 115/72 mmHg, pulse is 98/min, and respirations are 14/min. Physical exam reveals conjunctival icterus, bilateral flank tenderness, and erythema of the left leg. Laboratory workup is performed, and the results are shown below: Serum: Hemoglobin: 7.2 g/dL Total bilirubin: 2.1 mg/dL Direct bilirubin: 0.8 mg/dL Lactate dehydrogenase: 470 U/L Glucose-6-phosphate dehydrogenase: 7 U/gHb (normal: 6-20 U/gHb) Which of the following would most likely be seen on a peripheral blood smear in this patient?
Schistocytes
Codocytes
Acanthocytes
Degmacytes
Degmacytes
This patient presents with hemolytic anemia (low hemoglobin, elevated indirect bilirubin, and elevated lactate dehydrogenase) shortly after starting a sulfa medication (trimethoprim-sulfamethoxazole) in the setting of likely glucose-6-phosphate dehydrogenase deficiency. Degmacytes ("bite cells") will be seen on peripheral blood smears in these patients.

Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency will experience hemolytic anemia when exposed to an oxidizing substance such as sulfa drugs or fava beans. Laboratory tests will show a decrease in hemoglobin and hematocrit levels. Since hemolysis releases intracellular enzymes into the bloodstream, serum levels of lactate dehydrogenase will be increased. Hemoglobin is then metabolized in the spleen into unconjugated bilirubin, which will cause an elevated bilirubin level that is primarily indirect. In the acute setting, G6PD levels will be normal because the most compromised cells have all been hemolyzed. Obtaining a G6PD level in between episodes of hemolysis is therefore required to observe the chronically decreased G6PD in these patients. A peripheral blood smear will reveal degmacytes ("bite cells") and Heinz bodies. Avoidance of oxidative stress to red blood cells is the most important component of management in these patients.

Belfield and Tichy discuss the classic presentation of G6PD deficiency in patients. The authors review oxidizing medications such as rasburicase, primaquine, dapsone, pegloticase, and methylene blue. The authors recommend avoiding initiation of these medications whenever possible until a G6PD diagnostic test has been performed.

Incorrect Answers:
Answer A: Acanthocytes can be seen in patients with liver disease due to defective production of lipoproteins; however, these cells do not undergo acute hemolytic destruction. Patients with abetalipoproteinemia usually present with symptoms consistent with fat-soluble vitamin deficiency such as bleeding (vitamin K) or osteoporosis (vitamin D).

Answer B: Codocytes are most commonly seen in patients with thalassemia but can also generally be seen in all microcytic anemias. Patients with thalassemia will present with chronic anemia without acute episodes of hemolysis. The increased lactate dehydrogenase and bilirubin levels in this patient indicate an acute hemolytic event.

Answer D: Schistocytes can be seen in thrombotic thrombocytopenic purpura (TTP) and disseminated intravascular coagulation (DIC). Patients with TTP present with thrombocytopenia, microangiopathic hemolytic anemia, fever, neurologic symptoms, and acute kidney injury. DIC is a common downstream pathway for many processes such as sepsis, malignancy, and eclampsia; however, it would present with diffuse clotting and bleeding from all sites.

Answer E: Spherocytes can be seen in hereditary spherocytosis, which may result in hemolysis during times of acute stress; however, this patient denies symptoms of nausea, vomiting, or diarrhea. Instead, the hemolysis in response to new foods is most likely due to exposure to oxidizing substances such as trimethoprim-sulfamethoxazole.

Bullet Summary:
Patients with glucose-6-phosphate dehydrogenase deficiency will experience hemolytic anemia in response to oxidizing substances and will have degmacytes (bite cells) on peripheral blood smear.