A 40-year-old alcoholic man is being treated for tuberculosis, but he has been only intermittently compliant with his medications despite the health department’s best efforts at directly observed therapy. He complains of increasing weakness, fatigue, weight loss, and nausea over the preceding 3 weeks. He appears thin, and his blood pressure is 80/50 mm Hg. There is increased pigmentation over the elbows and in the palmar creases. Cardiac examination is normal. Which of the following is the best next step in evaluation?

**Core Concept**
The patient's symptoms of weakness, fatigue, weight loss, and nausea, combined with his history of alcoholism and non-compliance with tuberculosis treatment, suggest a potential case of drug-induced deficiency. Specifically, the increased pigmentation over the elbows and in the palmar creases is a classic sign of niacin deficiency, also known as pellagra.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with pellagra, a disease caused by a lack of niacin (vitamin B3) in the diet. Niacin is essential for energy production, nerve function, and maintaining healthy skin. The patient's non-compliance with tuberculosis treatment, which often includes isoniazid (INH), is a likely cause of his niacin deficiency. Isoniazid is known to interfere with niacin synthesis in the body, leading to a deficiency over time. The increased pigmentation over the elbows and in the palmar creases is a hallmark sign of pellagra, and the patient's thin appearance and low blood pressure are also consistent with advanced disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not address the patient's specific symptoms and signs, which are consistent with pellagra. While the patient's history of alcoholism and non-compliance with tuberculosis treatment may suggest other potential causes of his symptoms, the increased pigmentation over the elbows and in the palmar creases strongly suggests a diagnosis of pellagra.

**Option B:** This option is incorrect because it does not take into account the patient's history of alcoholism and non-compliance with tuberculosis treatment. While the patient's symptoms of weakness, fatigue, and nausea may suggest a diagnosis of anemia, the increased pigmentation over the elbows and in the palmar creases is a more specific sign of niacin deficiency.

**Option C:** This option is incorrect because it does not address the patient's specific symptoms and signs. While the patient's low blood pressure may suggest a diagnosis of hypotension, the increased pigmentation over the elbows and in the palmar creases is a more specific sign of pellagra.

**Option D:** This option is incorrect because it does not take into account the patient's history of alcoholism and non-compliance with tuberculosis treatment. While the patient's symptoms of weakness, fatigue, and nausea may suggest a diagnosis of malnutrition, the increased pigmentation over the elbows and in the palmar creases is a more specific sign of niacin deficiency.

**Clinical Pearl / High-Yield Fact**
Niacin deficiency can be prevented by supplementing with isoniazid (INH) with a daily dose of nicotinamide, which is a form of niacin that does not interfere with INH metabolism.

**Correct Answer:** C.

✓ Correct Answer: C. Early morning serum cortisol and cosyntropin stimulation