**Core Concept**
The child's presentation with pellagra-like dermatitis and aminoaciduria suggests a disorder affecting the metabolism of amino acids, possibly related to a deficiency in a specific enzyme involved in amino acid breakdown or utilization.

**Why the Correct Answer is Right**
The clinical features of pellagra-like dermatitis and aminoaciduria are characteristic of Hartnup disease, an autosomal recessive disorder caused by mutations in the SLC6A19 gene encoding the neutral amino acid transporter 1 (NAT1). This transporter plays a crucial role in the reabsorption of neutral amino acids in the kidneys, leading to their excessive excretion in the urine (aminoaciduria). The deficiency of tryptophan, an essential amino acid, due to impaired reabsorption, leads to a decreased production of niacin (vitamin B3), resulting in pellagra-like dermatitis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the clinical presentation described.

**Option B:** This option may be tempting, but it is not the correct answer, as the disorder described is related to amino acid metabolism and not directly to carbohydrate or fat metabolism.

**Option C:** This option is incorrect, as the disorder described is an autosomal recessive condition, not an X-linked disorder.

**Option D:** This option is not relevant to the clinical presentation described.

**Clinical Pearl / High-Yield Fact**
Hartnup disease is an autosomal recessive disorder, meaning that affected individuals are homozygous for the mutated gene, and both parents are usually carriers of the mutation.

**Correct Answer: C. Hartnup disease**