female patient with anemi...

An 80-year-old female patient visited a clinic with complaints of anemia. She maintained a balanced diet, and her vital signs were within normal limits. Upon examination, her tongue was severely atrophic, appearing red and smooth (Figure 1), but there were no neurological abnormalities. Her laboratory tests indicated megaloblastic anemia, with a hemoglobin level of 83 g/dL and a mean corpuscular volume of 110 fL. The cause of her condition was suspected to be vitamin B12 deficiency, confirmed by a vitamin B12 level of less than 50 pg/mL. Upper gastrointestinal endoscopy revealed the presence of Helicobacter pylori, which led to a diagnosis of vitamin B12 deficiency due to atrophic gastritis caused by the bacteria. Treatment began with intramuscular injections and oral administration of vitamin B12 after the H. pylori infection was treated. Within one month, the patient's glossitis and anemia significantly improved. What will be the diagnosis?