Fig. 11. Phytanic acid, its immediate precursors and metabolites, and site of enzyme defect in Refsum disease (Rd). (From Eldjarn L, Stokke O, Try K. In: Vinken PJ, Bruyn GW (eds). Biochemical aspects of Refsum's disease and principles for the dietary treatment. Handbook of Clinical Neurology. Amsterdam, North-Holland, 1976:519–541.)