Pernicious Anaemia: Mechanisms, Diagnosis, and Management

Abstract

Pernicious anaemia (PA) is an autoimmune disease of multifactorial aetiology involving environmental and immunological factors. It is the most common cause of cobalamin deficiency anaemia worldwide. The disease is a macrocytic anaemia caused by a vitamin B12 deficiency, which, in turn, is the result of intrinsic factor deficiency, a protein that binds avidly to dietary vitamin B12 and promotes its transport to the terminal ileum for absorption. Despite the advances in understanding the pathogenesis and molecular biology, diagnosis of PA is still challenging for clinicians because of its complexity, diverse clinical presentations, and the limitations of the available diagnostic tools for the evaluation of cobalamin status and the presence of chronic autoimmune atrophic gastritis. Asymptomatic autoimmune gastritis, a chronic inflammatory disease of the gastric mucosa, precedes the onset of corpus atrophy by 10–20 years. Diagnostic dilemmas could occur when patients with PA present with spuriously normal or high cobalamin levels, normocytic or microcytic anaemia, nonanaemic macrocytosis, autoimmune haemolytic anaemia, pseudo-thrombotic microangiopathy, hyperhomocysteinemia-associated thromboembolism, pseudoleukemia, bone marrow failure, and neurologic manifestations without anaemia or macrocytosis. Other autoimmune disorders, especially thyroid disease, Type 1 diabetes mellitus, and vitiligo, are also commonly associated with PA. The present review focusses on novel aspects regarding the pathogenesis, clinical presentation, and the diagnostic approach of PA; the true usefulness of serum vitamin B12 levels; and the risk of adenocarcinoma and gastric carcinoids as well as their treatment and monitoring strategies.