Pernicious Anaemia with Normal Vitamin B12

A 49-year-old female patient presented to our hospital with asthenia, odynophagia, low grade fever, worsening symptoms of chronic depression, and symmetric leg paresthesias. Investigations showed macrocytic anaemia, leucopenia, thrombocytopenia, high lactate dehydrogenase levels and a normal Coombs test. Trilineage dysplasia was detected in the bone marrow biopsy specimen. The diagnostic work-up led us to the diagnosis of pernicious anaemia with a spuriously normal value of vitamin B12 and high titres of anti-intrinsic factor autoantibodies. This case highlights the importance of considering vitamin B12 deficiency in the differential diagnosis of myelodysplasia, even when vitamin B12 levels seem to be normal. LEARNING POINTS: Vitamin B12 deficiency is characterized by neuropsychiatric manifestations and bone marrow failure with accompanying dysplastic changes. Spuriously normal vitamin B12 levels can occur in pernicious anaemia due to anti-intrinsic factor autoantibody interference in the laboratory assay. Myelodysplastic syndromes and vitamin B12 deficiency share clinical and laboratory similarities, so a correct differential diagnosis is crucial for adequate treatment.