Infantile Tremor Secondary to Vitamin B12 Deficiency: Case Report and Literature Review

Background: Adverse neurological outcomes have been associated with Vitamin B12 (Cobalamin) deficiency in infancy. The exact aetiology is unclear, but likely multifactorial. Interference with normal myelination, deranged s-adenosylmethionine production and aberrant cytokine regulation are postulated mechanisms in the literature.¹ Neurological manifestations of infantile B12 deficiency include poor feeding, hypotonia, developmental delay, tremor and seizures. Nutritional vitamin B12 deficiency is a treatable cause of neurologic dysfunction in infants.

Aim: We report an interesting case of tremor in an exclusively breastfed infant secondary to maternal Vitamin B12 deficiency.

Methods: The clinical findings, radiological imaging and blood profile of the index case were reviewed. The current available literature on vitamin B12 deficiency in the infantile period was evaluated.

Results: A 7 month term baby boy presented with a 2 month history of intermittent, symmetrical tremulous movements of his head, trunk and upper limbs. Neurological examination was unremarkable. Initial investigations including FBC, MCV, renal, liver, bone profiles and EEG were within normal limits. Urine organic acids revealed an elevated urinary methylmalonic acid (MMA) (266 umol/mmol (0-8umol/mmol)). Serum homocysteine was also raised (26mmol/l (0-11)). Serum Vitamin B12 was low (127ng/L (210-760)), with a serum folate (24 ug/l) within the normal range. His mother had a non-vegan diet, but was deficient in Vitamin B12 (163ng/L).

Conclusion: This case outlines a rare presentation of infantile tremor associated with functional Vitamin B12 deficiency. Maternal dietary deficiency is the most common cause of Vitamin B12 deficiency in infancy.¹ Methylmalonic acid and Homocysteine are more sensitive and specific indicators of vitamin B12 status than Mean Corpuscular Volume (MCV).² Prompt diagnosis and management of Vitamin B12 deficiency is essential to prevent significant irreversible neurological sequelae.

1. Smith J, Coman D (2014) Vitamin B12 Deficiency: an Update for the General Paediatrician. Pediat Therapeut 4: 188.

2. Rasmussen SA, Fernhoff PM, Scanlon KS. Vitamin B12 deficiency in children and adolescents. J Pediatr 2001;138:10--7