<prompt> Refsums disease is characterized by increased levels ofPhytanic acidAscorbic acidAcetic acidNone  <response>: Ans. a Phytanic acid. Ref. Harper, Biochemistry, 25th ed., 248REFSUMS DISEASE is a rare neurologic disorder due to a defect absent phytanic acid oxidase enzyme that causes the accumulation of phytanic acid, which is found in plant foodstuffs and blocks beta-oxidation.DISORDERS DUE TO PEROXISOMAL ABNORMALITIES Zellweger syndrome- Neonatal adrenoleukodystrophy- Infantile Refsum disease Hyperpipecolic acidemia- Acatalasemia- Adrenoleukodystrophy Pseudo-adrenoleukodystrophy- Hyperoxaluria type- Pseudo-Zellweger syndrome Rhizomelic chondrodysplasia punctata- Glutaryl-CoAoxidase deficiency Note: Zellweger syndrome is the most severe and infantile Refsum disease is the least severe form 