A 45-year-old man is admitted to the hospital for the evaluation of diplopia, weakness of his lower extremities, and gait difficulties. During the interview, the patient reveals that has been forcing himself to vomit after almost every meal over the last 6 weeks. He denies associated eye pain and discomfo, headache, or dysphagia. He has never experienced such symptoms in the past. Examination of the patient demonstrates slight disorientation, veical nystagmus worse on downgaze, diffuse weakness of the lower extremities, bilateral dysmetria, and hypothermia. Laboratory analyses reveal mild dehydration and hypokalemia. The patient’s status has improved after an administration of a vitamin. The physiologically active form of this vitamin acts as a coenzyme for which of the following enzymes?
A 45-year-old man is admitted to the hospital for the evaluation of diplopia, weakness of his lower extremities, and gait difficulties. During the interview, the patient reveals that has been forcing himself to vomit after almost every meal over the last 6 weeks. He denies associated eye pain and discomfo, headache, or dysphagia. He has never experienced such symptoms in the past. Examination of the patient demonstrates slight disorientation, veical nystagmus worse on downgaze, diffuse weakness of the lower extremities, bilateral dysmetria, and hypothermia. Laboratory analyses reveal mild dehydration and hypokalemia. The patient’s status has improved after an administration of a vitamin. The physiologically active form of this vitamin acts as a coenzyme for which of the following enzymes?
💡 Explanation
## **Core Concept**
The patient's symptoms suggest a neurological disorder likely caused by a nutritional deficiency, given the history of self-induced vomiting and laboratory findings of mild dehydration and hypokalemia. The key to solving this question lies in identifying the vitamin deficiency that could lead to such a clinical presentation and understanding its role as a coenzyme in various enzymatic reactions.
## **Why the Correct Answer is Right**
The patient's symptoms, including diplopia, weakness of the lower extremities, gait difficulties, vertical nystagmus, bilateral dysmetria, and hypothermia, along with improvement after vitamin administration, point towards a diagnosis of Wernicke-Korsakoff syndrome. This condition is caused by thiamine (Vitamin B1) deficiency. Thiamine, in its physiologically active form, thiamine pyrophosphate (TPP), acts as a coenzyme for several important enzymes. Among these, **transketolase** is a crucial enzyme in the pentose phosphate pathway, which is vital for generating NADPH and pentoses. Transketolase is particularly relevant because its activity is often used as a marker for thiamine deficiency.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While thiamine pyrophosphate (TPP) does serve as a coenzyme for pyruvate dehydrogenase, this option is not provided, making it an incorrect choice by default due to the specifics of the question.
- **Option B:** This option is not provided, but typically, enzymes like alpha-ketoglutarate dehydrogenase, another thiamine-dependent enzyme, might be considered. However, without the specific option, we focus on the accuracy of the correct answer.
- **Option C:** This would be incorrect because while there are several thiamine-dependent enzymes, the question specifically asks for an enzyme for which thiamine acts as a coenzyme, and the correct answer highlights transketolase.
- **Option D:** Without the specific details of this option, we acknowledge that the correct answer is focused on the role of thiamine in enzymatic reactions, specifically highlighting transketolase.
## **Clinical Pearl / High-Yield Fact**
A critical clinical pearl is that Wernicke-Korsakoff syndrome is a medical emergency. It presents with a classic triad of ophthalmoplegia (or nystagmus), ataxia, and altered mental status. Early recognition and treatment with thiamine can significantly improve outcomes, but delays can lead to irreversible Korsakoff psychosis.
## **Correct Answer:** .
✓ Correct Answer: D. Pyruvate dehydrogenase
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