Vitamin B₁₂ deficiency presenting with a pancytopenia in pregnancy

Vitamin B₁₂ deficiency is a significant public health problem globally. Although it is a well-known cause of macrocytic anaemia and in advanced cases, pancytopenia, there remains a relative paucity of cases reported in pregnancy. It is associated with an increased risk of pregnancy complications and adverse birth outcomes such as neural tube defects, preterm birth, low birth weight, neurological sequelae and intrauterine death. It has a predilection for individuals aged >60 years. It has been implicated in a spectrum of neuropsychiatric disorders and it may also exert indirect cardiovascular effects. Severe vitamin B₁₂ deficiency may present with haematological abnormalities that mimic thrombotic microangiopathy such as HELLP syndrome (haemolysis, elevated liver enzymes and low platelets) or it may present as pseudothrombotic microangiopathy (Moschcowitz syndrome) characterised by anaemia, thrombocytopenia and schistocytosis. It can also closely mimic thrombotic thrombocytopenia purpura, hence posing a diagnostic challenge to the unwary physician. Serological measurement of vitamin B₁₂ levels confirms the diagnosis. Oral supplementation with vitamin B₁₂ remains a safe and effective treatment. The authors describe the case of a multiparous woman in her late 20s presenting with a plethora of non-specific symptoms at 29⁺⁵ weeks' gestation. Her haemoglobin was 45 g/L, platelets 32×10⁹/L, vitamin B₁₂ <150 ng/L and serum folate <2 µg/L. She was not a vegetarian, but her diet lacked nutrition. Following parenteral B₁₂ supplementation, her haematological parameters improved. The pregnancy was carried to term. Due to the plethora of non-specific symptoms, the diagnosis can be challenging to establish. Adverse maternal or fetal outcomes may occur. Folic acid supplementation may mask an occult vitamin B₁₂ deficiency and further exacerbate or initiate neurological disease.