Overview 

Anaemia is a very common condition usually discovered in routine laboratory tests. Anaemia is a condition in which there is a decrease in red blood cells (RBC), the proportion of haemoglobin or the volume of packed RBCs (haematocrit). Haematocrit is the ratio of packed RBCs to blood volume. RBCs or erythrocytes contain haemoglobin, and their main function is to carry oxygen from the lungs to the body tissues and carbon dioxide from the body tissues to the lungs. There are many ways to classify anaemia, such as using mean corpuscular volume (MCV), a measure of the average volume of RBCs in a specimen. Low MCV indicates microcytic anaemia, normal MCV indicates normocytic anaemia, and high MCV indicates macrocytic anaemia. Normocytic indicates normal size of RBC, microcytic suggests RBCs of a smaller size, and macrocytic implies RBCs that are larger than normal. This may affect the body’s capacity for proper gas exchange. Anaemia may result from blood loss, increased destruction or reduced production of RBCs.¹ 

Common causes of normocytic anaemia

There are several reasons behind the aetiology of normocytic anaemia, and a minority of the cases reflect a primary disorder of the blood. Anaemia may be due to a chronic disease (inflammation, neoplasia), renal failure, endocrine failure (hypo- and hyperthyroidism), or bone marrow failure (red cell aplasia, aplastic anaemia, infiltration, and polymyalgia rheumatica).

Causes of acute blood loss

1. Gastrointestinal disturbances: Many conditions can cause blood loss, like peptic ulcer, Crohn’s disease, colon polyp and even tumours
2. Menstrual bleeding: People with heavy bleeding in conditions like fibroids, endometriosis
3. Trauma: Injuries caused due to accidents and increased blood loss
4. Surgery: One of the major complications is blood loss²

Increased RBC destruction (Haemolytic anaemia)

1. Hereditary spherocytosis: a defect in the RBC cell membrane means that the proper structure of the RBC cannot be maintained, leading it to rupture³
2. G6PD deficiency: Glucose-6-phosphate dehydrogenase deficiency may lead to increased oxidative stress and lead to cell destruction
3. Autoimmune haemolytic anaemia: antibodies are directed against the RBC and lead to its destruction⁴

Bone marrow disorders

1. Aplastic anaemia- a serious condition in which the bone marrow fails to produce the required blood cells ⁵ 
2. Myelodysplastic syndromes: a wide variety of blood disorders in which there is a cancer-like proliferation ⁶
3. Bone marrow infiltration: in which there is abnormal proliferation of cells in the bone marrow as a result of lymphoma, leukaemia and metastatic cancer

Endocrine disorders

1. Hypothyroidism - Thyroid is needed to produce erythropoietin, which is a precursor hormone involved in the production of erythrocytes (RBC). A decrease in thyroid levels may affect the production of RBCs⁷
2. Chronic adrenal insufficiency: hormonal disturbances in the adrenal gland can also lead to the defect in the erythropoietin synthesis⁸

 Chronic kidney disease

Erythropoietin is produced in the kidney; hence, erythropoietin deficiency is an indicator of kidney disease. The improper functioning of the kidney may lead to a reduction in hormone synthesis.

Combined nutritional deficiency

Iron, Folate and vitamin B12 may cause normocytic anaemia at an early stage and may later progress to other types of anaemia. 

Anaemia due to chronic disease

Most chronic disorders like inflammatory conditions, infections, neoplasms and various systemic diseases are associated with anaemia. Pathogenesis of chronic disease is multifactorial, and can be related to hypoactivity of the bone marrow, inadequate production of erythropoietin or poor response to erythropoietin, or poor survival rate of red blood cells.⁹

Diagnostic approach

1. History taking and physical examination: any history related to anaemia, like tinnitus, tiredness, palpitation, should be recorded. Checking for pallor/pale skin can be a clue
2. Blood test: red blood cell count, haemoglobin count
3. Reticulocyte count: This refers to the number of new, immature RBCs in the blood. A low count may indicate bone marrow failure
4. Peripheral blood smear: shows the size and shape of the RBCs, which may help diagnose the type of anaemia (micro-, macro- or normocytic)
5. Iron studies: usually low in iron deficiency anaemia, but in the early stages, show normocytic normochromic anaemia
6. Renal function test: to rule out chronic kidney disease
7. Bone marrow aspiration: to determine any bone marrow disorders 
8. Specific tests for the underlying conditions, like hormonal assays, liver function tests to determine kidney function

It is important to properly interpret the results of these tests to determine the cause of the anaemia and treat it accordingly.¹⁰ 

Commonly asked questions

How serious is normocytic anaemia?

The severity of normocytic anaemia depends on the severity of the underlying condition. For example, when a patient is suffering from bone marrow failure or if a person is having chronic kidney disease, then the anaemia is serious.

Is normocytic normochromic anaemia normal?

No, it is a type of anaemia in which the size and colour of the RBCs are normal, but the number of RBCs is fewer than normal. This results in improper transportation of oxygen to different parts of the body.

Can liver problems cause normocytic anaemia?

Yes, erythropoietin, important in erythropoiesis (red cell production), is produced from the liver.

Is normocytic anaemia curable?

Treatability depends on the cause of normocytic anaemia; thus, treatment depends on each individual case. 

Summary 

There are many different ways to classify anaemia. An important method of classification is based on the size of RBCs (microcytic, normocytic and macrocytic). There are many reasons for anaemia, for example, disturbance in the RBC production or destruction, and blood loss. Some reasons for normocytic anaemia include acute blood loss, chronic disease, some hormonal issues (which in turn affect the erythropoietin needed in RBC production), chronic kidney disease, haemolytic anaemias, and nutritional deficiencies. Anaemias may cause mild, moderate or even severe symptoms; thus, proper treatment is necessary at the earliest time possible to improve the patient’s quality of life.