BMJ Case Reports 2017; doi:10.1136/bcr-2016-218508
  • Reminder of important clinical lesson

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

  1. Kieran Anthony O’Connor
  1. Older Persons Specialist Health Services, Mercy University Hospital, Cork, Ireland
  1. Correspondence to Dr Sean James Farrelly, seanf88{at}
  • Accepted 14 July 2017
  • Published 17 August 2017


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.


  • Contributors The clinical cases were managed in the hospital setting by KAO’C. The idea for the article was taken equally by the listed authors. The literature review was performed by SJF. The article was initially written by SJF and reviewed and edited by KAO’C. The guarantor is KAO’C.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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