Vitamin B12 Deficit: An Unusual Presentation

Background: Vitamin B12 deficit is an uncommon cause of anaemia in children, but has the potential for severe haematological complications, like pancytopenia, severe anaemia or haemolysis.

Case Report: A 16-year-old, black male, previously healthy, presents to the emergency department with vomiting, abdominal pain and unquantified weight loss for one month. On the day of the admission, he started fever and was found prostrated with incoherent speech. Physical examination showed a Glasgow Coma Scale of 12, muco-cutaneous paleness, icterus in the sclera and hepatosplenomegaly. Laboratory investigation revealed pancythopenia (Haemoglobin 3g/dL, Leucocytes 2, 96x10^9/uL, Platelets 75x10^9/uL Reticulocytes 3,1%); high seric levels of indirect bilirubin (2,05 mg/dL N(0–0.8)), lactate dehydrogenase >5000 U/L (N135–225)) and aspartate aminotransferase (100 U/L (N8–40)). Peripheral blood smear showed anisocytosis, poikilocytosis, schistocytes, target cells, pencil cells and erythroblasts (25/100 leucocytes).

Uric acid, C reactive protein, ferritin and triglicerydes were normal, as well as the chest X-ray. Direct Coombs test was negative. Bone marrow aspiration ruled out leukaemia and normal levels of ADAMTS 13 excluded thrombocytopenic thrombotic purpura. Recent infection with Epstein-Barr virus, cytomegalovirus, or parvovirus B19 was also eliminated.

Low levels of vitamin B12 (146pg/mL (N 211–911)) were the only abnormality found, making this the likely cause of the severe anaemia, supported on clinical and haematological improvement upon supplementation with both vitamin B12 and folate, after immediate transfusion with 20ml/kg red blood cells.

Further investigation has yet to identify the cause of the deficiency, as pernicious anaemia, strict vegan diet, celiac sprue and inflammatory bowel disease have since been ruled out.

Conclusion: Vitamin B12 deficiency is a rare and treatable cause of pancytopenia. Like in this case, can mimmic leukaemia, hemophagocytic lymphohistiocytosis, and pseudothrombotic microangiopathy. This uncommon presentation is a reminder for clinicians to include vitamin B12 deficiency in the differential diagnosis of such findings.