<prompt> The Refsums disease in which there is accumulation of phytanic acid is due to defect ofCarnitine palmitoyl transferase-I deficiencyHMG-CoA lyase deficiencyb-oxidationa-oxidation  <response>: D a-oxidation Ref sums disease is a rare but severe neurological disorder. The patients of this disease accumulate large quantities of an unusual fatty acid, phytanic acid. It is derived from phytol, a constituent of chlorophyll. Hence it is found mostly in plants foods. However, it is also present in milk lipids and animal fats Phytanic acid cannot undergo 3-oxidation due to the presence of a methyl group on carbon-3. This fatty acid undergoes initial a-oxidation to remove the methyl group and this is followed by b-oxidation. Refsums disease is caused by faulty enzymes during the alpha-oxidation of phytanic acid resulting in buildup of phytanic acid and its unsaturated fatty acid derivatives in the plasma and tissues. Improved a-oxidation of branched chain fatty acids may be clue to deficiency of Phytanoyl-CoA hydraxylase or percxin-7 activities. 