Vitamin B12 Deficiency Presenting with Neurological Dysfunction in an Adolescent.

Background: Vitamin B12 deficiency is classically encountered in the adult Caucasian population and manifests as a subacute combined degeneration in the presence or absence of macrocytic anemia. However, B12 deficiency is extremely rare in children in developed countries, and pernicious anemia is even rarer etiology of this deficiency. The clinical presentation of B12 deficiency in children is not as easily recognizable or well-characterized and may result in missed or delayed diagnosis.

Patient Description: We describe a previously healthy adolescent girl who presented with emotional lability, mental status changes, hyperreflexia, and ataxia. She was found to have megaloblastic anemia and subacute combined degeneration secondary to B12 deficiency caused by pernicious anemia.

Conclusion: Though B12 deficiency is uncommon in pediatrics, it is important to maintain a high index of suspicion because early recognition and treatment of B12 deficiency are key to preventing long-term neurological sequelae.