Summary

Vitamin B₁₂ deficiency is a recognised pathology in several populations, with a particular prevalence in an older adult population. We present two cases whereby vitamin B₁₂ deficiency is the causative factor in marked pancytopaenia. Oval macrocytosis and hypersegmented neutrophils were noted on both peripheral blood samples, which are a characteristic finding in macrocytic anaemia due to B₁₂ deficiency. Distinct underlying pathologies were identified in both cases; food-cobalamin malabsorption and pernicious anaemia. Parenteral vitamin B₁₂ supplementation resulted in a marked reticulocytosis and rapid improvement of haematological indices in both cases. We present this series to serve as a reminder that B₁₂ deficiency can present as life-threatening pancytopaenia.It has has multiple underlying pathologies,defined risk populations and has characteristic blood film findings which can guide investigations, diagnosis and treatment.