What is the pathophysiologic mechanism of this patient’s fatigue

A 65-year-old previously well man presents to the clinic with complaints of fatigue of 3 months duration. Questioning reveals diffuse weakness and feeling winded when walking uphill or climbing more than one flight of stairs. All symptoms have slowly worsened over time. There are no other complaints, and the review of systems is otherwise negative. The patient has no significant medical history, social history, or family history. On physical examination, he appears somewhat pale, with normal vital signs. The physical examination is unremarkable except for his rectal examination, which reveals brown, guaiac-positive stool (suggesting the presence of blood in the stool). A blood test reveals anemia.

Answer the following questions with regard to the case study above:

a)  What is the most likely form of anemia in this man? What is the probable underlying cause?

b)  What is the mechanism by which this disorder results in anemia?

c)  What might one expect to see in the peripheral blood smear?

d)  What other tests might be ordered to confirm the diagnosis?

e)  What is the pathophysiologic mechanism of this patient’s fatigue, weakness, and shortness of b