Vitamin B12 deficiency presenting as acute ataxia: BMJ case
A previously healthy 7-year-old was hospitalised for evaluation of acute ataxia and failure to thrive, initially suspicious for an intracranial mass. Weight and body mass index were below the third percentile and he demonstrated loss of joint position and vibratory sense on examination.

Laboratory studies revealed megaloblastic anaemia while an initial MRI of the brain showed no evidence of mass lesions or other abnormalities. A dietary history revealed the child subscribed to a restrictive vegan diet with little to no intake of animal products or other fortified foods.

The child was diagnosed with presumed vitamin B12 deficiency and was treated with intramuscular B12 injections. Neurological symptoms resolved promptly within several days after starting therapy. This case underlines the importance of assessing nutritional status in the evaluation of neurological dysfunction in the pediatric patient.

Learning points
• Vitamin B12 deficiency is an uncommon but treatable cause of neurological dysfunction and failure to thrive in the pediatric population.

• Early recognition and treatment of the neurological manifestations of vitamin B12 deficiency is essential in ensuring full clinical recovery in developing children.

• Dietary assessments are crucial in the medical evaluation of all pediatric patients.

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