Refsum disease: A genetic disorder that affects the metabolism of the fatty acid phytanic acid. When phytanic acid accumulates, it causes a number of progressive problems, including inflammation of numerous nerves (polyneuritis), diminishing vision due to retinitis pigmentosa, and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain. Refsum disease is caused by mutations in
the PAHX gene on chromosome 10 that encodes the enzyme phytanoyl-CoA hydroxylase (PAHX). Also known as phytanic acid storage disease.
