The Refsum’s disease in which there is accumulation of phytanic acid is due to defect of
**Core Concept**
Refsum's disease is a rare genetic disorder characterized by the accumulation of phytanic acid, a branched-chain fatty acid, in the blood and tissues. This accumulation leads to a range of clinical symptoms, including peripheral neuropathy, retinitis pigmentosa, and cerebellar ataxia.
**Why the Correct Answer is Right**
The correct answer is related to the enzyme responsible for the breakdown of phytanic acid. Phytanic acid is oxidized to a 2-methyl-branched fatty acid by the enzyme phytanoyl-CoA hydroxylase, which is a part of the alpha-oxidation pathway. A defect in this enzyme leads to the accumulation of phytanic acid in the body. This enzyme is encoded by the PAH gene.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct enzyme involved in the breakdown of phytanic acid.
**Option B:** This option is incorrect because it is not related to the breakdown of phytanic acid.
**Option C:** This option is incorrect because it is related to a different metabolic pathway.
**Clinical Pearl / High-Yield Fact**
Refsum's disease is an autosomal recessive disorder, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease. The PAH gene is localized to chromosome 10p, and mutations in this gene have been identified as the cause of Refsum's disease.
**Correct Answer: D. Phytanoyl-CoA hydroxylase**