Severe Vitamin B12 Deficiency; an Unusual Cause of Developmental Regression in Infants

TI Yousif, PJ Shukla, S Gallagher 

University Hospital Limerick, Dooradoyle, Limerick, Ireland


Vitamin B12 deficiency is a rare, easily diagnosed, preventable cause of developmental delay or regression. A 10-month-old girl was admitted with recurrent choking episodes on solids. She was born at home and had no neonatal screening; no routine developmental clinic reviews and was unvaccinated. She had been exclusively breast fed since birth. Recurrent feeding difficulties prevented introduction of solid feeds. Mother was a strict vegan abstaining from the consumption of any animal products.

She presented pale, irritable, hypotonic and unable to sit without support. She had lost the ability to smile and to roll over. There was no babbling and no mouthing of objects reflecting absence of oral awareness. She was not reaching out for objects. There were no concerns in regards to vision or hearing. Her weight was in the 2nd percentile (6.9 kg) down from 25th centile at birth. Height and head circumference were both below the 9th centiles. Clinical examination was otherwise unremarkable.


Previously normal FBC, showed macrocytic anaemia with Haemoglobin of 8.3 g/dl and MCV of 115.5 fl. Folate level was normal, ferritin level was elevated at 275 ng/ml and B12 level was low with a value of 136 pg/ml [198-874]. Renal, liver and bone profile were normal. Metabolic workup showed high levels of homocysteine and markedly elevated urinary Methyl Malonic Acid (MMA), consistent with severe vitamin B12 deficiency. EEG showed mild encephalopathy. She was admitted for failure to thrive and developmental regression. Intramuscular vitamin B12 injections were started. She began fortified expressed breast milk administered via NG feeds. Referral to early intervention services for physiotherapy and speech and language therapy was made. Biochemical and clinical improvement was noted. She required NG feeds on discharge. Nasogastric feeds were successfully discontinued after several weeks. She had full recovery with no residual neurodevelopmental issues. Mother and siblings were diagnosed with B12 deficiency and received treatment. The family continued on vegetarian diet with addition of eggs and milk supported by dietician.

Vitamin B12 deficiency is a rare and treatable cause of failure to thrive and delayed development in infants1. In developed countries it is seen in exclusively breastfed infants, whose mothers have unrecognized pernicious anaemia or are strict vegans, causing low B12 levels in the infant at birth and in breast milk1. Two cases of weight loss and regression of motor skills caused by maternal vegan diet induced B12 deficiency have been reported. Severe vitamin B12 deficiency may lead to encephalopathy, failure to thrive, lethargy, and arrest or regression of developmental skills2, seizures3, pancytopenia, hypotonia and hyper pigmentation4. Elevated carnitine levels may be noted on neonatal screening. MMA level is reported to be more sensitive than serum B12.

This patient suffered due to lifestyle choice. Initially uncooperative regarding home NG feeds, mother agreed with help of social services. We recommend that vegan women take vitamin B12 supplementation during pregnancy and while breast-feeding. We would also suggest that all mothers with a lifestyle that might affect their children’s health receive adequate information regarding all possible risks.


Correspondence: Dr Taha I Yousif, Paediatrics department, Limerick University Hospital, Limerick, Co Limerick, Ireland

Tel +353 876329319

Email: [email protected]



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