This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
Refsum&;s disease is due to deficiency of which of the following enzyme? 
Select and explain. 
A. Malonate dehydrogenase, B. Thiophorase, C. Succinate thiokinase, D. Phytanic alpha oxidase
D: Phytanic alpha oxidase
Answer: D: Phytanic alpha oxidase 
Explanation: It is a metabolic error due to lack of alpha-hydroxylase (phytanic acid oxidase) so that alpha-oxidation does not occur and phytanic acid accumulates in the tissues. The patient presents with severe neurological symptoms, polyneuropathy, retinitis pigmentosa, nerve deafness and cerebellar ataxia. Regressions of symptoms are observed with restricted dietary intake of phytanic acid. Milk is a good source of phytanic acid, which may be avoided.Ref: DM Vasudevan, Page no: 135