PA15.1-3 | Macrocytic Anemias & B12/Folate — Graded Quiz

A 58-year-old strict vegetarian woman with a 20-year history of well-controlled Hashimoto's thyroiditis presents with 6 months of fatigue, difficulty walking on uneven ground, and tingling in both hands. CBC: Hb 8.4 g/dL, MCV 122 fL. Peripheral smear: macro-ovalocytes, hypersegmented neutrophils (6-lobed). Serum B12 = 58 pg/mL. Serum anti-parietal cell antibodies: positive. Anti-intrinsic factor (anti-IF) antibodies: positive. Which single test result MOST specifically establishes the cause of B12 deficiency in this patient?

A 34-year-old woman at 10 weeks gestation presents for her first antenatal visit. She reports a vegetarian diet and occasional dairy. CBC: Hb 11.4 g/dL, MCV 104 fL. Serum folate: 1.8 ng/mL (low; normal >3.0). Serum B12: 280 pg/mL (borderline). MMA: 0.18 µmol/L (normal <0.4). Homocysteine: 22 µmol/L (elevated; normal <15). She is started on folic acid 5 mg daily. Which ADDITIONAL action is MOST important at this visit?

A 67-year-old man with known pernicious anaemia stopped his monthly B12 injections 2 years ago after moving abroad. He now presents with progressive lower limb weakness and loss of balance. Examination: vibration sense absent at both ankles and knees, positive Romberg sign, bilateral extensor plantar responses (Babinski positive). Hb 9.8 g/dL, MCV 114 fL. Serum B12 = 42 pg/mL. He is started on B12 injections. After 6 months, his haemoglobin normalises. Which neurological outcome is MOST likely?

A peripheral blood smear from a 55-year-old patient with MCV 118 fL shows macro-ovalocytes and a neutrophil with 6 nuclear lobes. A second smear from a 60-year-old chronic alcohol user shows large, ROUND macrocytes (not oval), no hypersegmented neutrophils, and normal-looking lymphocytes. Serum B12 and folate are normal in the second patient. Which statement BEST explains why the smear findings differ between these two patients?

A 45-year-old woman with celiac disease presents with fatigue, sore tongue, and peripheral tingling. Labs: Hb 9.1 g/dL, MCV 96 fL (borderline). Peripheral smear: occasional macro-ovalocytes, 2 neutrophils with 5 lobes, 1 neutrophil with 6 lobes out of 100 counted. Serum B12 = 195 pg/mL (borderline low). Serum folate = low. Reticulocyte count = 0.6%. Which smear finding is the EARLIEST and MOST SENSITIVE indicator of megaloblastic change in this patient?

A 29-year-old woman with HIV on highly active antiretroviral therapy (HAART) including zidovudine (AZT) for 3 years develops macrocytic anaemia. CBC: Hb 10.2 g/dL, MCV 110 fL. Peripheral smear: round macrocytes. No hypersegmented neutrophils. Serum B12 and folate are both normal. Bone marrow: erythroid hyperplasia with megaloblastic-like changes in some precursors. Which mechanism BEST explains her macrocytosis?

A 70-year-old woman with confirmed pernicious anaemia presents with a 2-month history of diarrhoea, weight loss, and epigastric pain. Her B12 level (on injections) is now 650 pg/mL. Gastroscopy reveals a polypoidal lesion in the gastric fundus. Biopsy shows a well-differentiated neuroendocrine tumour (carcinoid). Which pathophysiological sequence BEST links her pernicious anaemia to this complication?

Two patients have megaloblastic anaemia. Patient A: serum B12 = 95 pg/mL, serum folate = normal, MMA = 0.85 µmol/L (elevated), homocysteine = 38 µmol/L (elevated). Patient B: serum B12 = normal, serum folate = 1.2 ng/mL (low), MMA = 0.19 µmol/L (normal), homocysteine = 31 µmol/L (elevated). A student offers to treat both patients with folic acid 5 mg daily. Which response is MOST appropriate?

A bone marrow aspirate smear from a 62-year-old woman with confirmed B12 deficiency (serum B12 = 65 pg/mL, Hb 8.2 g/dL, MCV 126 fL) shows: hypercellular marrow, erythroblasts with nuclei 2–3× normal size, lacy/open ('sieve-like') nuclear chromatin, well-haemoglobinised cytoplasm, and large 'giant metamyelocytes' in the granulocyte series. Which cellular process BEST explains the nuclear-cytoplasmic asynchrony?

A 52-year-old woman presents with fatigue and mouth soreness. Her CBC: Hb 7.9 g/dL, MCV 108 fL. Peripheral smear shows macro-ovalocytes and neutrophils with 6-lobed and 7-lobed nuclei. Serum B12 = 320 pg/mL (normal >200). Serum folate = normal. MMA = 0.61 µmol/L (elevated). Homocysteine = 29 µmol/L (elevated). Anti-IF antibodies: negative. She does not use alcohol. She is not on any medications. Her diet includes meat, eggs, and dairy. Which is the MOST likely underlying diagnosis?

A 38-year-old woman with celiac disease presents with a mixed picture: Hb 9.2 g/dL, MCV 88 fL (normal). Peripheral smear shows a dimorphic red cell population — some microcytic hypochromic cells (target cells, pencil cells) and some macro-ovalocytes — alongside a single neutrophil with 6 lobes. Serum ferritin = 5 ng/mL. Serum B12 = 110 pg/mL (low). The treating physician is puzzled by the normal MCV. Which mechanism BEST explains the normal MCV in the context of dual deficiency?

A 78-year-old man with Alzheimer's disease is brought by his daughter because of worsening confusion, falls, and 'electric shock' sensations in his legs with neck flexion (L'hermitte's sign). CBC: Hb 10.8 g/dL, MCV 102 fL. Peripheral smear: occasional macro-ovalocytes, 2 neutrophils with 5 lobes out of 100. Serum B12 = 198 pg/mL (borderline). MMA = 0.72 µmol/L (elevated). Homocysteine = 41 µmol/L (elevated). Which is the MOST APPROPRIATE next clinical action?