Riboflavin

Riboflavin is a water-soluble vitamin that must be acquired from the diet. Riboflavin uptake takes place through carrier-mediated absorption in the small intestine. Insight into human riboflavin transport and metabolism has expanded; currently, three inborn errors of riboflavin transport and metabolism are known. Riboflavin transporter deficiencies can present at all ages and cause a severe life-threatening neurodegenerative disorder. Timely treatment with oral riboflavin is highly effective and lifesaving. Deficiency of the mitochondrial flavin adenine dinucleotide (FAD) transporter has been reported to cause exercise intolerance with a good response to riboflavin supplementation. Mutations in the FLAD1 gene, which encodes FAD synthase, cause myopathy and respiratory chain dysfunction. In severely affected patients, this is a fatal disorder; however, patients with a milder course are potentially responsive to riboflavin.