Figure 1: Metabolic pathway of phytanic acid. Phytanic acid is derived from microbial degredation of the phytol side chain of chlorophylls ingested by ruminants, invertebrates, or pelagic fish. In humans the source is phytol from diet chlorophyll, or from meat, pelagic fish, or diary. When digested it is in-cooperated into chylomicrons/VLDL and then transported to liver and tissues for further metabolism. Most fatty acids are metabolised by -oxidation pathways in peroxisomes and mitochondria. ⋆ denotes the enzyme deficient in patients with Refsum disease. # denotes the alternate less efficient -oxidation pathway.