Anaemia: Overview

Abstract Anaemia, a decrease in erythrocyte mass that is reflected in a reduction in the haemoglobin concentration in the peripheral blood, is the most common haematologic condition for which medical attention is sought. Erythrocytes are critical to tissue oxygenation and carbon dioxide removal, and severe anaemia may lead to tissue hypoxia and organ dysfunction. Erythropoiesis is a highly regulated process controlled by erythropoietin. Adaptive mechanisms permit moderate anaemia to be well tolerated, and the clinical importance of mild to moderate anaemia is its representation of an underlying disease. Mild to moderate anaemia may be one of the first clues of an underlying disease. Although many of the signs and symptoms of anaemia are nonspecific, a pragmatic classification of anaemia based on integration of kinetic and morphologic characteristics of erythrocytes allows efficient investigation of the underlying aetiology. Key Concepts Anaemia is the most common haematologic condition encountered in medical practice Erythrocytes are critical to tissue oxygenation and carbon dioxide removal Physiologic compensatory mechanisms allow mild to moderate anaemia to be well tolerated; severe anaemia may be associated with tissue hypoxia and organ dysfunction Erythropoiesis, the production of erythrocytes, is a tightly regulated process controlled predominantly by the synthesis of erythropoietin in response to hypoxia The clinical significance of mild–moderate anaemia lies in its association with an underlying systemic disease; the finding of anaemia should prompt consideration of additional investigations Classification of anaemia based on kinetic and morphologic erythrocyte characteristics allows pragmatic segregation into microcytic, macrocytic or normocytic anaemia, further directing the investigation of an underlying disease