Hypersegmented neutrophils and oval macrocytes in the setting of B12 deficiency and pancytopaenia.

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.