Neonatal vitamin B12 deficiency secondary to maternal subclinical pernicious anemia:: Identification by expanded newborn screening

A neonate with elevated propionylearnitine on the newborn screen was found to have methvlmalonic acidemia due to vitamin B-12-deficiency. The mother was also vitamin B,,-deficient. This case illustrates the utility of expanded newborn screening for detection of vitamin B,, deficiency, allowing prompt treatment and prevention of potential sequelae.