Vitamin B12 deficiency with severe brain involvement in childhood: the importance of early diagnosis

Abstract

Introduction: Vitamin B12 deficiency in early childhood is a treatable cause of neurological impairment, yet it is often overlooked. While it usually presents with hematological abnormalities, in some infants neurological symptoms may represent the first or even the only clinical manifestation, delaying diagnosis. Case report: We describe a 17-month-old male infant with developmental regression, progressive pallor, feeding refusal, and marked somnolence. Laboratory tests revealed pancytopenia and low vitamin B12 levels. Brain CT and MRI showed cortical atrophy and delayed myelination. Intramuscular cyanocobalamin therapy was initiated, resulting in rapid hematologic recovery and partial improvement of motor milestones. Subsequent investigations identified Helicobacter pylori infection as a likely cause of malabsorption, which resolved after eradication therapy. Follow-up demonstrated clinical improvement and neurological stabilization. Discussion: This case underscores the importance of considering vitamin B12 deficiency in infants presenting with neurological regression, even in the absence of early hematological abnormalities. Clinical response largely depends on the interval between symptom onset and supplementation. Early intervention can prevent permanent sequelae, whereas delayed diagnosis is frequently associated with a poorer prognosis. Conclusion: Vitamin B12 deficiency should be included in the differential diagnosis of developmental regression in infants, particularly when nutritional or gastrointestinal risk factors are present. Early recognition and timely supplementation are essential to improve outcomes and prevent irreversible neurological damage.