A 35-year-old male who is homeless is admitted with a
history of breathlessness and swelling of his ankles. On examination there is
peripheral oedema, he is in atrial fibrillation, has an elevated JVP,
displaced apex beat, a third heart sound, reversed splitting of the second
heart sound and a soft systolic murmur at the apex.
You take a detailed dietary history in this patient, as
you are aware that this condition may be caused by deficiency of: