Lesh-Nyan syndrome is due to deficiency of: (Repeat)
**Core Concept**
Lesh-Nyan syndrome, also known as Sjögren-Larsson Syndrome, is a rare genetic disorder characterized by ichthyosis, spastic dementia, and other neurological abnormalities. It is caused by a deficiency of the enzyme fatty aldehyde dehydrogenase (FALDH), which is crucial for the breakdown of fatty aldehydes in the skin and brain.
**Why the Correct Answer is Right**
The deficiency of FALDH leads to the accumulation of toxic fatty aldehydes, causing damage to the skin and brain. This results in the characteristic symptoms of ichthyosis, spasticity, and cognitive impairment. The enzyme FALDH is a crucial component of the fatty aldehyde pathway, and its deficiency disrupts normal lipid metabolism.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the enzyme deficiency associated with Lesh-Nyan syndrome is not related to glycolysis.
* **Option B:** This option is incorrect because the deficiency of the enzyme responsible for Lesh-Nyan syndrome is not related to the metabolism of branched-chain amino acids.
* **Option C:** This option is incorrect because the deficiency of the enzyme responsible for Lesh-Nyan syndrome is not related to the breakdown of aromatic amino acids.
**Clinical Pearl / High-Yield Fact**
Lesh-Nyan syndrome is a rare genetic disorder caused by a deficiency of the enzyme fatty aldehyde dehydrogenase (FALDH). It is characterized by ichthyosis, spastic dementia, and other neurological abnormalities, and is often associated with a characteristic "waxy" appearance of the skin.
**Correct Answer:** D.