Pernicious anemia is not the only kind of macrocytic anemia. Other causes of abnormally large red blood cells include:
the long-term use of certain medications and antibiotics, such as methotrexate and azathioprine
chronic obstructive pulmonary disease
chronic alcoholism
folate (vitamin B-9) deficiency caused by poor diet or disorders that affect absorption
Other causes of vitamin B-12 deficiency, such as poor diet, are often confused with pernicious anemia. Pernicious anemia is strictly an autoimmune disorder resulting from a lack of IF. Pernicious anemia is also seen in children who are born with a genetic defect that prevents them from making IF.