RESUMO
This case report describes an 18-month-old male presenting with hemolytic anemia and lethargy, who was ultimately diagnosed with severe vitamin B12 deficiency. The child exhibited global developmental delays, including a lack of speech and walking skills. Initially suspected as intravascular hemolytic anemia, the normal reticulocyte count led to further investigation, which revealed low cobalamin (vitamin B12) levels. The patient received vitamin B12 injections, resulting in normalized cobalamin levels. Additional evaluations ruled out metabolic disorders and other etiologies for his anemia. Follow-up laboratory testing showed improved hemoglobin levels, and the patient was discharged with plans for close monitoring. The case emphasizes the importance of considering vitamin B12 deficiency in children, particularly those with developmental delays and anemia. Early diagnosis and treatment are crucial for preventing long-term neurological consequences associated with severe and prolonged cobalamin deficiency. Healthcare professionals should be aware of the impact of nutrient deficiencies on growth, development, and brain maturation in pediatric populations.