adult Refsum disease obsolete Refsum disease true This class was intended for representing the union of infantile and adult Refsum diseases, but these are distinct with no genetics or phenotypes in common. OBSOLETE. A rare autosomal recessive condition caused by mutation(s) in the PHYH gene, encoding phytanoyl-CoA dioxygenase, peroxisomal. It is characterized by abnormalities in the breakdown of phytanic acid and impaired growth of myelin sheaths. Signs and symptoms include neurologic damage, cerebellar degeneration, and neuropathy. MONDO:0021665