PA H4 | Macrocytic Anemias & B12/Folate — Practice Quiz

A 54-year-old woman presents with progressively worsening fatigue, a sore, red tongue, and tingling in both feet. Her CBC shows Hb 7.2 g/dL, MCV 118 fL, and WBC 4.1 × 10⁹/L. Peripheral smear reveals macro-ovalocytes and neutrophils with 6-lobed nuclei. Serum B12 is 78 pg/mL (normal >200). Serum folate is normal. Which single additional investigation is MOST specific for confirming the underlying etiology of her B12 deficiency?

Intrinsic factor (IF), secreted by gastric parietal cells, is essential for B12 absorption. At which anatomical site does the IF–B12 complex bind to a specific receptor to enable absorption?

A peripheral blood smear from a patient with macrocytic anaemia is shown. The key findings are oval macrocytes (macro-ovalocytes) and a neutrophil with 7 nuclear lobes. Which of the following is the MOST likely diagnosis?

A 38-year-old vegan man presents with fatigue, glossitis, and MCV 122 fL. Serum B12 is low; serum folate is normal. Laboratory testing shows markedly elevated serum methylmalonic acid (MMA) and mildly elevated homocysteine. Which metabolic pathway explains the elevated MMA in B12 deficiency?

A 68-year-old woman with a history of total gastrectomy 5 years ago presents with fatigue and a haemoglobin of 8.1 g/dL, MCV 110 fL. Serum B12 is 60 pg/mL. Which mechanism BEST explains her B12 deficiency?

A patient has MCV 105 fL with macrocytic anaemia. Serum B12 is 180 pg/mL (borderline low). Serum folate is normal. Serum MMA is 0.28 μmol/L (normal <0.4). Serum homocysteine is 14 μmol/L (normal <15). Which is the MOST appropriate conclusion?

A 35-year-old pregnant woman at 28 weeks gestation presents with fatigue and pallor. CBC: Hb 9.4 g/dL, MCV 108 fL, platelets 142 × 10⁹/L. Serum folate is markedly reduced; serum B12 is normal; MMA is normal; homocysteine is elevated. Which statement BEST explains why folate demands are increased in pregnancy?

A 62-year-old man with a 30-year history of heavy alcohol use presents with MCV 104 fL. His peripheral smear shows round macrocytes but NO hypersegmented neutrophils and NO macro-ovalocytes. Serum B12 and folate are both normal. LFTs show elevated GGT and AST. Which is the MOST likely cause of macrocytosis in this patient?

A 45-year-old woman is found to have B12 deficiency on routine screening. She has no neurological symptoms. She is vegetarian but not vegan and eats eggs and dairy products regularly. Anti-parietal cell antibodies are weakly positive; anti-intrinsic factor antibodies are negative. Serum B12 is 142 pg/mL. What is the MOST likely cause of her B12 deficiency?

A 58-year-old man known to have pernicious anaemia presents to the emergency department with acute onset of bilateral leg weakness, loss of vibration sense at the ankles, and a positive Romberg sign. His B12 injections were stopped 18 months ago when he 'felt better.' Hb is 10.2 g/dL, MCV 116 fL. Which condition BEST explains his neurological findings?

A laboratory workup on a 48-year-old woman with macrocytic anaemia returns: serum B12 = 120 pg/mL (low), serum folate = normal, MMA = markedly elevated, homocysteine = markedly elevated. A second patient has: serum B12 = normal, serum folate = low, MMA = normal, homocysteine = markedly elevated. Which statement about the biochemical differences between these two patients is CORRECT?

A second-year MBBS student studying a bone marrow aspirate from a patient with B12 deficiency notes very large erythroid precursors with open, lacy (sieve-like) nuclear chromatin, even though the cytoplasm is well haemoglobinised. The granulocyte precursors are also very large ('giant metamyelocytes'). Which cellular mechanism BEST explains these findings?