I am going to answer the sample USMLE Step 1 Questions with Explanation. These questions are available at USMLE.org
A 53-year-old man comes to the physician because of a dry scaly rash on his body for the past year. He has had a 15-kg (33-lb) weight loss during the past year. He is 178 cm (5 ft 10 in) tall and now weighs 54 kg (120 lb); BMI is 17 kg/m2. His stools have a large volume and float. Which of the following nutrient deficiencies is most likely?
(A) Magnesium
(B) Vitamin A
(C) Vitamin B12 (cobalamin)
(D) Vitamin C
(E) Zinc
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Answer
The patient’s presentation suggests malabsorption, which can cause deficiencies in fat-soluble vitamins (A, D, E, K). Given the symptoms:
- Dry, scaly rash: This can be a sign of vitamin A deficiency, which affects the skin’s ability to maintain moisture and integrity.
- Weight loss and low BMI indicate a chronic issue, such as malabsorption, which can lead to fat-soluble vitamin deficiencies.
- Large, floating stools Suggest steatorrhea, a hallmark of fat malabsorption.
Vitamin A is crucial for maintaining healthy skin and mucosal surfaces. When deficient, the skin becomes dry, scaly, and rough. In contrast, zinc deficiency typically causes acrodermatitis enteropathica, a rash localized around body orifices and extremities, which is less consistent with the described symptoms.
The correct answer is B