a 35 year old man was hospitilized 3 months after returning from a 1 month visit to puerto rico. he had a recent history of watery

a 35 year old man was hospitilized 3 months after returning from a 1 month visit to puerto rico. he had a recent history of watery diarrhea, anorexia, 30lb weight loss, and progressively severe weakness. he had a megaloblastic anemia with panctopenia. serum folate was 7.5 nmol/L (normal 15-45nmol/L), an dserum vitamin B12 was 27pmol?l (111-663 pmol/L). the patient was found ot have malabsorption of folate and vitamin B12. he was treated with tetracycline, which caused cessation of diarrhea. three years later he was hospitalized with the same symptoms. once again he was found to have megaloblastic changes and a pancytopenia. pharmacologic doses of folate and vitamin B12 resulted in a hematologic and clinical remission. why does the patient have a pancytopenia?