Which of the following clinical laboratory observations is suggestive of Hartnup disease?
**Core Concept**
Hartnup disease is a rare **autosomal recessive disorder** characterized by impaired **neutral amino acid transport** across the intestinal mucosa and renal tubules. This condition affects the body's ability to absorb certain amino acids from the diet.
**Why the Correct Answer is Right**
The correct answer is related to the clinical manifestations of Hartnup disease, which include **pellagra-like symptoms** due to **niacin deficiency**. This deficiency occurs because tryptophan, an amino acid affected by the transport defect, is a precursor to niacin.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the pathophysiology of Hartnup disease.
**Option B:** Similarly, this option does not accurately describe a key feature of the disease.
**Option C:** This option is also incorrect as it does not align with the known clinical or laboratory findings in Hartnup disease.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that Hartnup disease can lead to **neurological symptoms** and **dermatitis** due to the deficiency of essential amino acids and niacin.
**Correct Answer:** D. Aminoaciduria