**Core Concept**
Pellagra is a disease characterized by the symptoms of dermatitis, diarrhea, dementia, and potentially death, caused by a deficiency of niacin (vitamin B3) or tryptophan. The disease is often associated with inadequate dietary intake of tryptophan, an essential amino acid that can be converted into niacin in the body.

**Why the Correct Answer is Right**
Tryptophan is an essential amino acid that plays a crucial role in the synthesis of niacin. In the presence of adequate tryptophan, the body can convert it into niacin, which is essential for maintaining healthy skin, nerves, and the digestive system. A deficiency in tryptophan can lead to a decrease in niacin levels, resulting in the development of pellagra-like symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the development of pellagra-like symptoms. Histidine is another essential amino acid, but its deficiency does not directly impact niacin levels.
**Option B:** This option is incorrect because it does not accurately describe the cause of pellagra-like symptoms. Methionine is a non-essential amino acid that can be synthesized by the body, and its deficiency does not lead to niacin deficiency.
**Option C:** This option is incorrect because it does not accurately describe the cause of pellagra-like symptoms. Leucine is a branched-chain amino acid that is not directly involved in the synthesis of niacin.

**Clinical Pearl / High-Yield Fact**
The conversion of tryptophan to niacin is a critical step in maintaining healthy skin and nerves. A deficiency in tryptophan can lead to the development of pellagra-like symptoms, which can be prevented by ensuring adequate dietary intake of tryptophan or supplementing with niacin.

**Correct Answer:** D.