What condition might be indicated by elevated MCV and low haemoglobin in an elderly man with anaemia?

Elevated mean corpuscular volume (MCV) along with low hemoglobin typically suggests the presence of macrocytic anemia, which is often due to vitamin B12 deficiency or folate deficiency. In this scenario, vitamin B12 deficiency is particularly relevant, especially in elderly individuals, as absorption issues related to aging, dietary insufficiency, or gastrointestinal disorders can lead to this deficiency.

Vitamin B12 is crucial for DNA synthesis, and its deficiency results in ineffective erythropoiesis, leading to the production of larger-than-normal red blood cells, hence the elevated MCV. The low hemoglobin indicates anemia. Symptoms might also include neurological manifestations, which can further differentiate vitamin B12 deficiency from other types of anemia.

Other conditions such as iron deficiency anemia typically present with microcytic anemia (low MCV) rather than macrocytic, making them less likely in this context. Normocytic anemia might occur with chronic disease or acute illness, but it does not explain the elevated MCV. Thus, considering the combination of elevated MCV and low hemoglobin in an elderly man, vitamin B12 deficiency stands out as the most likely condition.