Rare Diseases Linked to Mutations in Vitamin Transporters Expressed in the Human Blood–Brain Barrier

Recent advances have significantly enhanced our understanding of the role of membrane transporters in drug disposition, particularly focusing on their influence on pharmacokinetics, and consequently, pharmacodynamics. The relevance of these transporters in clinical pharmacology is well acknowledged. Recent research has also underscored the critical role of membrane transporters as targets in human diseases, including their involvement in rare genetic disorders. This review focuses on transporters for water-soluble B vitamins, such as thiamine, riboflavin, and biotin, essential cofactors for metabolic enzymes. Mutations in transporters, such as SLC19A3 (thiamine), SLC52A2, and SLC52A3 (riboflavin), and SLC5A6 (multiple B vitamins including pantothenic acid and biotin) are linked to severe neurological disorders due to their role in the blood–brain barrier, which is crucial for brain vitamin supply. Current treatments, mainly involving vitamin supplementation, often result in variable response. This review also provides a short perspective on the role of the transporters in the blood-cerebrospinal fluid barrier and highlights the potential development of pharmacologic treatments for rare disorders associated with mutations in these transporters.