Diagnosis and treatment of vitamin B12 deficiency in children.

Vitamin B12 deficiency is a common yet frequently underrecognized nutritional disorder with important public health implications, particularly in low- and middle-income countries where maternal deficiency, vegetarian dietary practices, and food insecurity are prevalent. In children, deficiency may lead to irreversible neurodevelopmental impairment, growth failure, and hematological abnormalities, making early recognition essential. The clinical spectrum ranges from asymptomatic biochemical deficiency and isolated macrocytic anemia to developmental regression, seizures, movement disorders, peripheral neuropathy, and pancytopenia, with neurological manifestations often preceding hematological changes. Diagnosis requires integration of clinical features with laboratory evaluation, including complete blood count, peripheral smear, serum vitamin B12 estimation, and functional biomarkers such as methylmalonic acid and homocysteine, which improve diagnostic accuracy in borderline or atypical cases. Molecular testing has expanded the identification of inherited disorders affecting vitamin B12 absorption and metabolism, enabling timely lifelong management. Prompt replacement therapy is the cornerstone of treatment and should not be delayed when clinical suspicion is high. Oral supplementation is effective for most dietary deficiencies, whereas parenteral therapy is indicated for severe anemia, neurological involvement, malabsorption, or inherited cobalamin disorders. Early treatment results in rapid hematological recovery, but delayed intervention may leave permanent neurological sequelae despite biochemical correction. Beyond individual patient care, strengthening maternal nutrition, targeted screening of high-risk populations, food fortification, and public awareness are critical strategies to reduce the burden of vitamin B12 deficiency and prevent avoidable disability. This review summarizes current evidence on the diagnosis and treatment of pediatric vitamin B12 deficiency and highlights practical approaches for improving clinical outcomes.