Archive Of Standardized Exam Questions: Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency


This page is dedicated to organizing various examples of standardized exam questions whose answer is glucose-6-phosphate dehydrogenase (G6PD) deficiency. While this may seem a odd practice, it is useful to see multiple examples of how glucose-6-phosphate dehydrogenase (G6PD) deficiency will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a tradition question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a disease is quite valuable.


When it comes to standardized exams, each topic has its own “code” marked by key buzzwords, lab findings, clues, etc. If you are well versed in this code you will be able to more quickly identify the condition that is being discussed, and get the right answer on the exam you are taking. Below is the “code” for G6PD deficiency

Chief Complaints:

  • Dark urine: caused by hemolysis
  • Jaundice can also be present

Patient History:

  • Recent medication usage: certain medications are associated with precipitating this condition/hemolysis
    • Antimalarial medications (such as chloroquine) are common!
    • Antibiotics (such as dapsone)

Clinical Workup:

  • Anemia: present on CBC.
  • Evidence of hemolysis: increased LDH, decreased haptoglobin, increased bilirubin
  • Heinz bodies (blood smear): darkly staining regions within red blood cells. Very specific to this condition!
    • Bite cells can also be present
  • Prussian blue positive urine: stains for hemosiderin. Present during hemolytic crises with this condition.

Question # 1

A 5 year old boy is brought to the clinic because of feeling fatigued for the past 3 weeks. The patient has also has had an acute onset of fever and chills about 3 hours ago. One month ago, the patient had his family traveled to Asia. He received chloroquine prophylaxis prior to this trip. Physical examination is remarkable for pallor and splenomegaly. His hematocrit is 21%, leukocyte count is 18,5000/mm³, and platelet count is 75,000/mm³. Blood smears are conducted and show the presence of darkly staining regions within the red blood cells. What is the most likely diagnosis in the patient?

Explanation # 1

Chloroquine medication administered + anemia + heinz bodies on blood smear = glucose-6-phosphate dehydrogenase (G6PD) deficiency

Question # 2

A 25 year old male is treated with an antibiotic for a urinary tract infection. A few days later he comes to the clinic for a follow up visit. He explains that his urinary symptoms from the infection have mostly resolved, however he now has dark appearing uirne. His past medical history is unremarkable, and he does not use any tobacco or alcohol. His temperature is 98.4°F, pulse is 85/min, respirations are 15/min, and blood pressure is 125/75 mm Hg. A physical exam is within normal limits. The patients urine sample stains positive with Prussian blue and a urine sediment is unremarkable. What is the likely diagnosis in this patient?

Explanation # 2

Recent new antibiotic usage (for UTI) + dark urine + Prussian blue positive urine = (G6PD) deficiency

Question # 3

A 30 year old male is on his way to travel to Africa to visit family and friends. He is given the appropriate vaccinations and prophylactic medications prior to his trip. A week later he presents to the emergency department with jaundice and complaints of dark urine. Labs are collected and are shown below:

  • Hemoglobin: 8.0 g/dL ***
  • Reticulocytes: 7.8%
  • Total bilirubin: 3.8 mg/dL
  • Direct bilirubin: 1.0 mg/dL
  • Lactate dehydrogenase (LDH): 350 U/L
  • Haptoglobin: 40 mg/dL (ref range: 50-150 mg/dL)

A peripheral smear is conducted and stain. It reveals the presence of darkly staining regions within the patient’s red blood cells. What is the likely diagnosis in this patient?

Explanation # 3

Malaria prophylaxis (for Africa trip) + dark urine + anemia +  heinz bodies on blood smear = (G6PD) deficiency

Question # 4

A 26 year old male comes to the clinic because he has been feeling fatigued, is jaundiced, and dark urine. His past medical history is notable for HIV with a CD4 count of 190. A few days ago he was started on dapsone for PCP prophylaxis. Labs are conducted and are notable for a hemoglobin of 8.5 g/dL and a reticulocyte count of 7.5%. A peripheral blood smear is notable for red blood cell fragments, as well as the presence of “bite” cells. What is the likely diagnosis in this patient?

Explanation # 4

Dark urine + recent antibiotic usage (dapsone) + anemia + bite cells = (G6PD) deficiency

Question # 5

A 25 year old male comes to the clinic because he has had multiple episodes of jaundice, dark urine, and anemia. When gathering the history, his physician notices that these episodes only occur after the patient begins taking certain drugs. A peripheral blood smear is conducted and it is shown below.

Image source

What is the likely diagnosis in this patient?

Explanation # 5

Dark urine + anemia + precipitated by certain drugs + bite cells = (G6PD) deficiency

Question # 6

A 32 year old male is diagnosed with a urinary tract infection and is given sulfamethoxazole/trimethoprim.  His past medical history is unremarkable, and he takes no other medications. Soon after beginning his antibiotic therapy, he develops anemia and notices that his urine has darkened. What is the likely diagnosis in this patient?

Explanation # 6

Recent usage of antibiotics + anemia + dark urine  = (G6PD) deficiency

Question # 7

A 35 year old male works internationally and is given prophylaxis for malaria due to upcoming recent travels. He then becomes jaundiced and lab tests demonstrate the presence of hemolytic anemia. What is a possible diagnosis in this patient?

Explanation # 7

Malaria prophylaxis + jaundice + hemolytic anemia = (G6PD) deficiency


Many questions on standardized exams go beyond simply recognizing the underlying topic. Often there are specific testable facts regarding some aspect of the topic’s pathophysiology/management/clinical implications that are commonly asked. Some of these are listed below:


  • Enzyme deficiency: of G6PD
  • Inheritance pattern: x-linked recessive condition.
  • What does G6PD do? It is the rate limiting step of the pentose phosphate pathway (PPP). Catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconolactone.
  • Why is PPP important? Is responsible for making NADPH which is required for making glutathione.
  • What does Glutathione do? it help neutralize free radicals.
  • So overall what does deficiency of G6PD do? Make red blood cells more susceptible to damage by free radicals. Leads to hemolysis.


Page Updated: 11.06.2016