Vitamin B12 (Cobalamin): Its Fate from Ingestion to Metabolism with Particular Emphasis on Diagnostic Approaches of Acquired Neonatal/Infantile Deficiency Detected by Newborn Screening

Acquired vitamin B12 (vB12) deficiency (vB12D) of newborns is relatively frequent as compared with the incidence of inherited diseases included in newborn screening (NBS) of different countries across the globe. Infants may present signs of vB12D before 6 months of age with anemia and/or neurologic symptoms when not diagnosed in asymptomatic state. The possibility of identifying vitamin deficient mothers after their pregnancy during the breastfeeding period could be an additional benefit of the newborn screening. Vitamin supplementation is widely available and easy to administer. However, in many laboratories, vB12D is not included in the national screening program. Optimized screening requires either second-tier testing or analysis of new urine and blood samples combined with multiple clinical and laboratory follow ups. Our scope was to review the physiologic fate of vB12 and the pathobiochemical consequences of vB12D in the human body. Particular emphasis was put on the latest approaches for diagnosis and treatment of vB12D in NBS.

Automated summary

Compared to the incidence of inherited diseases in newborn screening, acquired vitamin B12 deficiency is relatively frequent in newborns. Infants may present anemia and/or neurologic symptoms before 6 months of age if not diagnosed in an asymptomatic state. Newborn screening can also help identify vitamin deficient mothers during pregnancy and breastfeeding. Vitamin supplementation is widely available and easy to administer. However, vitamin B12 deficiency is often not included in national screening programs. Optimized screening requires second-tier testing or analysis of new urine and blood samples, along with multiple clinical and laboratory follow ups.