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Review Question - QID 210466

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QID 210466 (Type "210466" in App Search)
A 42-year-old woman presents to her primary care physician for fatigue and blurry vision. She is a refugee from Syria who arrived in the United States 1 week ago. She has lived for the last 8 months in a refugee camp. She worked at a grocery store in Syria before being displaced from her home. She has one son who is 9 years old and was seen by a pediatrician the day prior. She reports that while she was in the refugee camp, she ate very little and gave most of her food to her son to ensure that he stayed healthy. She denies any past medical history and takes no medications. She does not smoke or drink alcohol. Her temperature is 97.8°F (36.6°C), blood pressure is 108/68 mmHg, pulse is 102/min, and respirations are 18/min. On exam, she appears fatigued but is fully cooperative with the examination. There are fissures at the corners of her mouth. A slit lamp examination reveals corneal vascularization in both eyes. Her tongue is darkly erythematous. This patient is most likely deficient in a vitamin that has which of the following functions?

Cofactor for homocysteine methyltransferase

7%

5/68

Cofactor for pyruvate dehydrogenase enzyme

6%

4/68

Precursor to FAD and FMN

71%

48/68

Constituent of NAD+ and NADP+

6%

4/68

Component of coenzyme A

6%

4/68

Select Answer to see Preferred Response

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The patient in this vignette presents with a history of malnutrition and cheilosis, corneal vascularization, and a magenta-colored tongue suggestive of riboflavin deficiency. Riboflavin is a precursor compound to FAD and FMN.

Riboflavin (vitamin B2) is a water-soluble vitamin that has multiple functions including being a cofactor for redux reactions and a precursor to FAD and FMN. Riboflavin deficiency may arise in the setting of severe malnourishment and as a result, will often co-present with other vitamin deficiencies. Specific findings seen in riboflavin deficiency include cheilosis (inflammation of the lips and fissures at the corners of the mouth), corneal vascularization, and a magenta-colored tongue.

Incorrect Answers:
Answer 1: An important cofactor for homocysteine methyltransferase is vitamin B12 (cobalamin). Vitamin B12 deficiency may present with a macrocytic, megaloblastic anemia, hypersegmented neutrophils, and neurologic symptoms due to myelin degeneration.

Answer 2: An important cofactor for the pyruvate dehydrogenase enzyme is vitamin B1 (thiamine). Vitamin B1 deficiency may present with Wernicke syndrome (ataxia, confusion, and nystagmus), Korsakoff syndrome (confabulation, psychosis, and mammillary body hemorrhage), peripheral neuropathy (e.g., dry beriberi), or high-output cardiac failure (e.g., wet beriberi). FAD is a cofactor for the pyruvate dehydrogenase complex, but not the enzyme itself. Rather, it is a cofactor for the dihydrolipoyl dehydrogenase enzyme.

Answer 4: An important constituent of NAD+ and NADP+ is vitamin B3 (niacin). Vitamin B3 deficiency may present with the pellagra, which is characterized by the triad of diarrhea, dermatitis, and dementia.

Answer 5: An important component of coenzyme A is vitamin B5 (pantothenate). Vitamin B5 deficiency is rare but may present with dermatitis, enteritis, alopecia, and adrenal insufficiency.

Bullet Summary:
Riboflavin is a key precursor to flavin coenzymes (FAD and FMN) and a deficiency of riboflavin may present with cheilosis, corneal vascularization, dry skin, and a magenta-colored tongue.

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