Vitamin B12 deficiency in children in a high-income country: clinical features and outcomes from a 10-year retrospective study

Background Vitamin B12 deficiency in children can cause severe hematological and neurological complications, yet epidemiological data from high-income countries remain limited. This study aimed to characterize the clinical, hematological, and etiological features of vitamin B12 deficiency in children referred to a pediatric hematology center in a high-income country. Methods A retrospective single-center study was conducted at a pediatric hematology clinic in Northern Italy, analyzing data collected over a 10-year period. Children with serum vitamin B12 levels ≤250 pg/mL were included. Patients were stratified by total vitamin B12 into very low (≤100 pg/mL), low (101–200 pg/mL), and marginal (201–250 pg/mL) B12 levels. Clinical, laboratory, and etiological data were analyzed. Results Of 461 eligible patients, 8.6% had serum B12 levels ≤250 pg/mL. The median age was 12 years, with a bimodal distribution peaking in infants/toddlers (35%) and adolescents (53%). The main referral reasons were anemia (52.5%), hemoglobinopathy traits (15%), isolated macrocytosis (10%), pancytopenia (12.5%), and CNS involvement (17.5%). Patients with B12 levels ≤100 pg/mL had significantly lower hemoglobin concentrations and higher biochemical markers of ineffective erythropoiesis compared to other groups. Conclusions Vitamin B12 deficiency should be systematically considered in the differential diagnosis of unexplained cytopenias and neurological manifestations in pediatric patients, particularly in specialized hematology settings. In our cohort, serum B12 concentrations ≤100 pg/mL were associated with more pronounced hematological abnormalities and frequently observed among patients with neurological involvement; however, this finding does not establish a validated pediatric severity threshold. Early recognition and prompt treatment are essential to prevent potentially irreversible complications.