Severe Vitamin B12 Deficiency in an Exclusively Breastfed 9-month-old Infant

Background: Vitamin B12 deficiency is an important and in lots of cases an under recognized cause of neurological morbidity in infants. The main cause of vitamin B12 deficiency in exclusively breastfed infants is maternal deficiency.

Objective: We present an infant with hypotonia, developmental retardation and cerebral atrophy due to vitamin B12 deficiency.

Case presentation: An exclusively breastfed 9-month-old female infant, who was born after a normal full-term pregnancy, was hospitalized due to failure to thrive, apathy, hypotonia, developmental retardation and cerebral atrophy on MRI scan. The child showed normal developmental features up to 6 months, but after then the parents recognized that their baby became less active, stopped communicating and had refusal of solid food. Upon admission, her weight, height and head circumference were dropped down more than 2 major percentile lines, she was hypotonic, apathetic, lacking smiling and presenting involuntary movements. She had a hemoglobin level of 9,1g/dl with an MCV of 99,5fl. The results of metabolic examinations revealed elevations in Methylmalonic Acid (183.4 mmol/mol creatinine, normal value <2.5) and Homocysteine (157.90 μmol/L, normal value 6.10-9.22). Furthermore, her serum vitamin B12 level was 50pg/ml (normal value 211-911) and serum folate level >20ng/ml (normal value 4.6-18.7). Her mother’s vitamin B12 level was 163pg/ml. The child was diagnosed as having vitamin B12 deficiency due to maternal deficiency and was treated with intramuscular vitamin B12 injections. After the initiation of vitamin B12, the infant developed severe involuntary movements and seizures. Antiepileptics were introduced in addition to Vitamin B12 and seizures disappeared. After a few days clinical improvement was observed with an achievement of developmental milestones, but she still showed significant delayed neuropsychiatric development.

Conclusion: Vitamin B12 deficiency should be considered in all infants with developmental retardation and hypotonia because early identification and treatment can prevent irreversible brain injury.