Chapter 146. Introduction

Vitamins are organic molecules that are present in trace amounts in the diet and that act as coenzymes (eg, pyridoxine), or coenzyme precursors (eg, riboflavin and thiamine). Several inborn errors that respond dramatically to treatment with vitamins are described in the following sections.

The mechanisms that underlie how different conditions respond to vitamins are quite varied. Some mutations reduce absorption of a vitamin(s) across the intestinal mucosa, others limit transport between the gut and other tissues, and yet others impair their incorporation into coenzymes (eg, vitamin B12 into adenosyl- and methyl-B12) or holoenzymes (eg, biotin into holocarboxylases). Mutations in catalytic proteins may reduce their interactions with their coenzymes, and in pyridoxine-dependant seizures, an accumulated compound binds pyridoxine and makes it unavailable as a coenzyme. In yet other cases, as in biotin-responsive basal ganglia disease, the mechanism of vitamin responsiveness is unknown.

Because treatment of these conditions is specific and possibly lifesaving, it is important that they be thought of and recognized early in patient evaluation.