Question.

Which one of the following is NOT a cause of macrocytic anaemia ?

  1. Alcohol abuse
  2. Hyperthyroidism
  3. Methotrexate
  4. Phenytoin
  5. Gastrectomy


Answer.

b

Explanation.

Causes of enlarged red blood cells (macrocytosis – MCV, typically >100 femtoliters) include:

  1. Vitamin B12 deficiency (pernicious anaemia, gastrectomy or gastric bypass surgery – all causing impaired intrinsic factor secretion and consequent failure of vitamin B12 absorption)
  2. Folate deficiency (poor diet, pregnancy, malabsorption syndromes)
  3. Alcohol abuse
  4. Hypothyroidism
  5. Drugs (e.g. phenytoin, methotrexate and the cytotoxic chemotherapeutics)
  6. Reticulocytosis due to severe haemolytic anaemia
  7.