In developed countries, the
vitamin B12 deficiency usually occurs in children exclusively breast-fed, whose mothers are vegetarians, causing low stores of
vitamin B12. Symptoms of
vitamin B12 deficiency appear during the second trimester of life and include
failure to thrive,
lethargy,
hypotonia, and arrest or regression of developmental skills. A
megaloblastic anemia can be present. One half of the infants exhibit
abnormal movements before the start of treatment with intramuscular
cobalamin, which disappear 1 or 2 days after. More rarely,
movement disorders appear a few days
after treatment, whereas neurological symptoms are improving. These
abnormal movements can last for 2 to 6 weeks. If not treated,
vitamin B12 deficiency can cause lasting neurodisability. Therefore, efforts should be directed to preventing deficiency in pregnant and breast-feeding women on
vegan diets and their infants by giving them
vitamin B12 supplements. When preventive supplementation has failed, one should recognize and treat quickly an infant presenting with
failure to thrive and delayed development.