Refsum disease is a rare genetic disorder caused by a deficiency in the enzyme phytanoyl-CoA hydroxylase. This enzyme is essential for breaking down a type of fat called phytanic acid, which accumulates in the body when the enzyme is not functioning properly. Symptoms can include vision problems, hearing loss, and issues with movement due to nerve damage. The condition is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the faulty gene to develop the disease. Diagnosis often involves measuring levels of phytanic acid in the blood, and treatment may include dietary restrictions to limit phytanic acid intake.