What is the difference between microcytic and macrocytic

Due to the larger sizes of red blood cells, there are low numbers of red blood cells in the blood. Thus, this causes low levels or insufficient levels of hemoglobin per cell. Red blood cells become larger when they fail to produce DNA quickly enough to divide at the right time as they grow. Therefore, macrocytic anemia most commonly occurs as a result of megaloblastic anaemia.

Moreover, macrocytic anemia can be caused due to liver disease, hemoglobinopathies, metabolic disorders, marrow disorders and increased destruction. Microcytic anemia is the condition of having smaller red blood cells than normal while macrocytic anemia is the condition in which the red blood cells are larger than the normal size. So, this is the key difference between microcytic and macrocytic anemia. Moreover, another difference between microcytic and macrocytic anemia is that microcytic anemia mainly occurs due to the deficiency of haemoglobin production, such as iron deficiency or thalassaemia, while macrocytic anemia mainly occurs due to the problems with the synthesis of the blood cells, as in vitamin B12 or folic acid deficiency.

Microcytic anemia is characterized by smaller red blood cells, having a small MCV value below 80 fL. In contrast, macrocytic anemia is characterized by too larger red blood cells, having a large MCV value above fL. In both conditions, the blood has low levels of hemoglobin.

Iron deficiency is the most common cause of microcytic anemia while megaloblastic anaemia is the most common cause of macrocytic anemia. NICE has issued rapid update guidelines in relation to many of these.

This guidance is changing frequently. Macrocytosis means that the red blood cells are larger than normal. Macrocytic anaemia occurs when there is also a fall in haemoglobin levels in the blood. Anaemia is usually defined as a haemoglobin level of at least two standard deviations below the mean for that age and sex. By this definition, 2. Children have a lower haemoglobin than adults. As a general rule, macrocytosis occurs when there are problems with the synthesis of the blood cells, as in vitamin B12 or folic acid deficiency, whilst microcytosis is associated with deficiency of haemoglobin production, such as iron deficiency or thalassaemia.

New cells, especially reticulocytes, are also slightly larger and so, if they occur in excessive numbers, there may be macrocytosis. The term macrocytosis describes the presence of macrocytes on a blood film, together with a raised mean corpuscular volume MCV.

It is a common finding in the results of an FBC and may or may not be associated with an anaemia. Macrocytosis may occur as a laboratory artefact, perhaps following incorrect storage of the sample.

A spuriously raised MCV may also occur due to cold agglutinins, paraproteins as in myeloma, hyperglycaemia or marked leukocytosis. Macrocytic anaemia describes a macrocytosis associated with a reduced haemoglobin and most commonly occurs as a result of a megaloblastic anaemia.

Macrocytic anaemia can be classified as megaloblastic and non-megaloblastic. Megaloblastic refers to a characteristic abnormality of the erythroblasts in the bone marrow in which the maturation of the nucleus is delayed relative to the cytoplasm.

It results from defective DNA synthesis. The liver has abundant stores of vitamin B12 and so, if absorption is impaired, it takes 4 or 5 years for deficiency to develop. Macrocytosis per se does not cause any symptoms or signs but there may be features related to the underlying disease. Mild anaemia may be asymptomatic.

Most cases are diagnosed when a blood count is performed as part of an investigation for something other than features of anaemia.

People who are older or have coronary heart disease are more likely to have symptoms, whilst the young can be remarkably anaemic and not complain. Overt high-output cardiac failure can occur.

Physical signs also depend upon the degree of anaemia and may include:. The term pernicious anaemia emphasises that onset is slow and gradual. These cells are predisposed to splenic degradation, leading to extravascular hemolysis.

Physical findings include jaundice and splenomegaly, while laboratory tests are consistent with hemolytic anemia.

The definitive treatment for HS is splenectomy. Patients have episodic hemolysis when cells encounter oxidative stressors. Aplastic anemia AA : rare life-threatening condition characterized by pancytopenia and hypocellularity of the bone marrow, in the absence of any abnormal cells, reflecting damage to the hematopoietic stem cells HSCs.

Aplastic anemia can be acquired or inherited. Multiple causes are known, including autoimmune damage to HSCs, medications, chemicals, whole-body radiation, viral infections, immune diseases, pregnancy, Fanconi anemia, and Down syndrome. Autoimmune hemolytic anemia: rare type of hemolytic anemia characterized by the production of autoantibodies directed against RBCs, leading to the destruction of these cells in the spleen.

The etiology is diverse and includes infections, autoimmune diseases, lymphoproliferative disorders, and drugs. Paroxysmal nocturnal hemoglobinuria PNH : rare and serious acquired chronic hemolytic anemia HA with periodic exacerbations.

The underlying defect is a somatic mutation in a multipotent hematopoietic stem cell of the X-linked PIGA gene, followed by clonal expansion of the mutated stem cells. These abnormal RBCs undergo mostly intravascular hemolysis and may form a part of a unique clinical triad that also includes pancytopenia and venous thrombosis.

References Auerbach, M. Causes and diagnosis of iron deficiency anemia in adults. Diagnostic approach to anemia in adults. Overview of hemolytic anemias in children. Diagnosis of hemolytic anemia in adults. Red blood cell and bleeding disorders. In Kumar, V. Robbins and Cotran Pathologic Basis of Disease, 7th ed.

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Defective heme synthesis: Iron deficiency anemia Lead poisoning Defective globin chains: Hemoglobinopathies, including sickle cell anemia Thalassemias. Fatigue Generalized weakness Loss of appetite Cold hands or feet Restless legs Pica eating nonfood substances like ice or clay.