Hanup disease is mainly due to:
**Core Concept**
Hanup disease, also known as Hartnup disease, is a rare genetic disorder affecting the body's ability to absorb certain amino acids from the diet. It is characterized by a defect in the transport of neutral amino acids in the kidneys and intestines. This condition is caused by mutations in the SLC6A19 gene, which codes for a neutral amino acid transporter.
**Why the Correct Answer is Right**
The correct answer is related to the genetic basis of Hanup disease. The SLC6A19 gene is responsible for encoding the neutral amino acid transporter responsible for the reabsorption of neutral amino acids in the kidneys and intestines. Mutations in this gene lead to impaired transport of these amino acids, resulting in the symptoms associated with Hanup disease. The defective gene affects the kidneys' ability to reabsorb amino acids, leading to their excessive excretion in the urine.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not related to the genetic basis of Hanup disease.
**Option B:** Incorrect because it is not the primary cause of Hanup disease.
**Option C:** Incorrect because it is not the correct gene associated with Hanup disease.
**Clinical Pearl / High-Yield Fact**
Hanup disease is characterized by a defect in the transport of neutral amino acids, which can lead to a characteristic skin rash and neurological symptoms. It is essential to consider this condition in patients presenting with these symptoms, especially if they have a family history of similar disorders.
**Correct Answer: C. SLC6A19 gene.