system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
An old man having complaint of anorexia, weakness and paraesthesia. On investigation, his haemoglobin was 5.8g% and peripheral smear showed macrocytes and neutrophils having hypersegmented nuclei. His tendon reflexes were also sluggish. Endoscopy revealed atrophic gastritis. Deficiency of which of the following factor can lead to this situation
assistant
The correct answer is  Diagnosis of the patient is pernicious anemia. Factors favouring this diagnosis are:

Megaloblastic anemia.
Demyelination (decreased tendon reflexes)
Atrophic gastritis

So, he would require B12 supplementation.