A woman with macrocytic anaemia and confusion

An 82 year old woman with a history of type 2 diabetes presented with unsteady gait and confusion of two months’ duration. Her diabetes was controlled by metformin (500 mg, three times a day) and she had no other comorbidities. She was a non-smoker and did not drink alcohol. Dietary history showed an adequate intake of meat, vegetables, and calories.

On examination, her vital signs were stable. She was disorientated in time but not in person or place. Cranial nerve examination was normal but examination of the peripheral nervous system showed ataxia and impaired proprioception of the lower limbs bilaterally. The rest of her examination was normal. Her score on the mini-mental state examination at presentation was 18 out of 30.

Blood tests showed: haemoglobin 55 g/L (reference range 120-150), white blood cell count 3.9×10⁹/L (4-10), neutrophils 2.4×10⁹/L (2-7), lymphocytes 1.4×10⁹/L (1-3), red blood cell count 1.22×10¹²/L (3.8-4.8), mean cell volume 133 fL (84-96), platelets 127×10⁹/L (150-400), bilirubin 28 µmol/L (1-19) (all other liver function tests were normal), lactate dehydrogenase 31.7 µkat/L (2.3-3.6). Her haptoglobin was <0.08 g/L (0.58-2.43) and vitamin B₁₂ and serum folate were 61.2 pmol/L (138-651.5) and 13.6 nmol/L (6.8-38.5), respectively. Absolute reticulocyte count was 6×10⁹/L (50-100). Ferritin was raised at 605.8 pmol/L ng/mL (22.5-449.4). Antiparietal cell antibodies and anti-intrinsic factor antibodies were negative. A peripheral blood smear showed hypersegmented neutrophils and oval macrocytes. A megaloblastic picture was seen on bone marrow biopsy, with no evidence of dysplastic features.

No abnormality was seen on computed tomography of the brain, and oesophagogastroduodenoscopy and biopsy showed no evidence of gastritis.