A 30-year-old male presents with abdominal pain and diarrhea. His blood test shows a hemoglobin of 9 g/dL and MCV of 110 fL. What could be the potential causes, and what are the next steps?
This patient's anemia with a high MCV (macrocytic anemia) could suggest vitamin B12 or folate deficiency, which can be associated with malabsorptive disorders such as celiac disease or Crohn's disease that might explain his gastrointestinal symptoms. Another possibility is medication effect (e.g., methotrexate, antiretroviral therapy). Checking vitamin B12 and folate levels would be a logical next step. In addition, a gastrointestinal evaluation, including possible endoscopy or colonoscopy, may be indicated.