Introduction

Anaemia is defined as a condition in which there is a decrease in the number of red blood cells (RBCs), the proportion of haemoglobin, or the collective volume of packed red blood cells.¹ It is possible to classify anaemia based on the mean corpuscular volume (MCV) of the red blood cells, which is the average size of red blood cells in a specimen. Red blood cells are called microcytic when the MCV is low  (red cell MCV < 80 femtolitres (fL)), normocytic when the MCV is normal  (red cell MCV 80 fL – 100 fL), and macrocytic when the MCV is higher than normal  (red cell MCV > 100 fL).² In general, anaemia is defined as haemoglobin levels less than 13.0 g/dL in men and less than 12.0 g/dL in premenopausal women.³

Normocytic normochromic anaemia is a form of anaemia where the RBCs are of normal size and normal colour, indicating that the haemoglobin content in each red blood cell is within normal limits. In normocytic normochromic anaemia RBCs typically appear similar to a normal red cell under the microscope. Occasionally, variations in size and shape may equalise one another, resulting in average values within normal limits. Miscellaneous chronic infections and systemic diseases are the most common causes of normocytic normochromic anaemia. 

The majority of normocytic anaemias appear to be caused by impaired RBC production.⁴ Majority of normochromic normocytic anaemias are caused by other diseases; a minority results from problems primarily of blood itself. 

Major contributors to normocytic normochromic anaemia are:

1. Infections 18% to 95% 
2. Cancer 30% to 77% 
3. Autoimmune disorders 8% to 71% 
4. Organ rejection 8 to 71% 
5. Chronic kidney disease 23% to 50% 

Data on less common causes like endocrine or marrow failure and acute blood loss remain limited.⁶ 

However, in this article, we will focus on some infections leading to Normocytic anaemia such as HIV, Tuberculosis, And Parasitic Infections.

Common symptoms of normocytic anaemia include

It is important to note that the effects of normocytic anaemia can vary from mild to severe, depending on the red blood cell count and any medical conditions that may exacerbate the symptoms. Anaemic symptoms can develop gradually if the disease is slowly progressing, but they can worsen suddenly if it progresses rapidly.^8,9 

Some of the common symptoms are:

• Fatigue, low energy 
• A general feeling of being weak 
• Headaches
• Lack of motivation
• Dizziness 
• Pale skin
• Brain fog (difficulty with concentration and memory)

The symptoms of normocytic anaemia are numerous, although mild anemia may only cause a few, if any, of these symptoms to occur.⁸ Furthermore, the following are some important history questions regarding normochromic normocytic anaemia:

• Diet
• Pain in the abdomen, reflux disease, and peptic ulcer disease
• Medicines, such as the use of nonsteroidal anti-inflammatory drugs
• An autoimmune condition or a history of cancer
• Blood loss, including menstrual history (eg, passage of blood with stools or urine)
• Family history of thalassemia or sickle cell disease

HIV and normocytic anaemia

Among HIV-positive individuals, anaemia is the most common blood-related abnormality seen. Anaemia indicates the prognosis in people living with HIV, and is associated with disease progression, reduced quality of life, and mortality.¹⁰ Anaemia in HIV may be caused by infections, neoplasms, or drug treatments, particularly zidovudine.¹¹ 

There are three basic mechanisms involved in HIV-associated anaemia: 

• Decreased RBC production 
• Increased RBC destruction 
• Ineffective RBC production⁷ 

Anemia can manifest as a mere laboratory abnormality without any symptoms in some HIV-positive individuals, but others may experience typical symptoms (e.g., fatigue, dyspnea, reduced exercise tolerance, and diminished functional capacity) directly related to a reduction in haemoglobin concentration.^5,11 Furthermore, there are several risk factors commonly associated with anaemia in HIV, including advanced HIV disease, low CD4 lymphocyte count, high viral load, the presence of an opportunistic infection, female gender, and lower body mass index (BMI).¹⁰

Tuberculosis and normocytic anaemia

As an airborne disease, tuberculosis (TB) induces systemic inflammation. Chronic cough, sputum production, loss of appetite, weight loss, fever, night sweats, and coughing out blood with sputum are typical clinical symptoms of pulmonary tuberculosis (PTB). It is common for patients with active PTB to have low haemoglobin, and anaemia is the most common comorbidity associated with TB.^12,13,14 According to research, patients with tuberculosis (TB) are likely to suffer from anaemia of chronic disease (ACD) and iron deficiency anaemia (IDA), whose prevalence rates are 49.82% and 20.17. 

Furthermore, patients' quality of life and treatment outcomes are affected significantly by low haemoglobin (Hb) levels at the time of TB diagnosis or as the infection progresses. Recurrent TB infection is more likely to occur in individuals with low Hb levels. People with TB often develop anaemia as a result of chronic inflammation and iron deficiency as the disease progresses.¹⁵ It is common for anaemic patients to have elevated levels of chemicals called cytokines, which are indicators of ongoing inflammation. In parallel, hepcidin, a protein that is involved in the metabolism of iron, is markedly increased in chronic infections and inflammatory states, contributing to disrupted iron metabolism in anaemia of chronic disease (ACD). A significant increase in hepcidin levels has been shown in TB cases as compared with non-TB controls, suggesting that it can be used as a diagnostic tool. 

Risk factors for anaemia in people with TB are similar to those associated with anaemia in HIV-positive adults. These are low body mass index (BMI), HIV infection with high retroviral load, worm infestations, low selenium concentrations, old age, high cytokine (IL-6) concentrations, and female gender.¹²

Parasitic infections and normocytic anaemia

The literature indicates that anaemia was more commonly observed in individuals infected with parasites such as E. histolytica, G. lamblia, A. duodenale, T. trichiura, and A. lumbricoides, with hookworm (A. duodenale) being particularly associated with lower haemoglobin levels due to blood loss. Several factors may contribute to anaemia, including parasitic blood loss, nutritional deficiencies, or poor hygiene, especially among female farmers and young people. 

In addition to mild iron deficiency without microcytosis, factors such as folate or B12 deficiency and hemoglobinopathies also contribute to this condition. 

Summary

Normocytic normochromic anaemia is marked by red blood cells that are normal in size and haemoglobin content but reduced in number, which is typically caused by chronic infections rather than primary blood disorders. Infections like HIV and tuberculosis (TB) are major contributors. In HIV-related anaemia, RBC production is decreased, RBC destruction is increased, and erythropoiesis is ineffective, whereas TB induces anaemia through chronic inflammation, elevated cytokines, and increased hepcidin levels. Parasitic infections such as A. duodenale, E. histolytica, and G. lamblia cause anaemia mainly through blood loss and nutrient deficiencies. References