A 59-year-old man had 3 months of unexplained chronic diffuse abdominal pain. Results of upper and lower endoscopy, abdominal-pelvic CT, and urinalysis were unremarkable; hemoglobin level was 8.7 g/dL; peripheral blood smear showed basophilic stippling of erythrocytes; and physical examination showed bluish pigmentation along the gingival margin. What is the diagnosis and what would you do next?
