Macrocytic Anaemia: Not Always a Straightforward Diagnosis.

Macrocytosis is defined as a mean corpuscular volume greater than 100 femtolitres (fL). There are several causes for macrocytic anaemia, and they can be divided into megaloblastic or non-megaloblastic anaemia. Vitamin B12 deficiency is one of the most common causes of megaloblastic anaemia. The cause of vitamin B12 deficiency must be evaluated including the presence of pernicious anaemia as it could alter the treatment and follow-up. Pernicious anaemia can be associated with other autoimmune diseases constituting polyglandular syndromes.