Primary immunodeficiency: what is it?

Primary immunodeficiencies mainly affect the immune system in children and adults and increase the risk of contracting frequent and particularly serious infections.

According to the latest figures, there are approximately 6 million people with primary immune deficiencies worldwide. What are they and how to treat them? We explain to you.

What is primary immunodeficiency?

Primary immune deficiencies include up to 250 diseases characterized mainly by a total or partial loss of the functions of the immune system.

The immune system is made up of a complex network of cells, tissues and organs distributed throughout the body such as blood, lymph nodes, bone marrow, liver, spleen, intestine, etc. The seamless functioning of this assembly protects the human body from pathogenic microorganisms such as bacteria, viruses and fungi that can cause disease and strengthen the body's defense mechanisms.

When the dysfunction of the immune system is of genetic origin, we speak of primary immunodeficiency.

The main forms of immunodeficiency are hereditary and occur in the first months after birth. In some cases, even congenital, immunodeficiency does not become clinically evident until adulthood.

Subjects with PID are unable to produce antibodies, also called immunoglobulins, hence the state of hypogammaglobulinemia or agammaglobulinemia that characterizes these diseases. It is precisely the lack of production of immunoglobulins that increases the increased susceptibility of patients to infections, the severity of which essentially depends on the type of immunodeficiency from which they suffer.

Symptoms of primary immunodeficiency in children

Frequent and serious infections such as sepsis, meningitis and complicated pneumonia at an early age should raise alarm bells about the risks of primary immunodeficiency.

Infections and in particular those of the upper respiratory tract such as rhinitis, otitis or bronchitis are also present in immunologically normal children. They mainly result from viral infections and are considered physiological. A child can catch the pathogen, become ill and recover permanently.

In children with primary immunodeficiency, infections tend to recur more frequently and more severely.

Infections can easily become complicated: recurrent ear infections can be purulent, episodes of bronchopneumonia, lack of reactivity to antibiotics, etc.

The presence of chronic diarrhea, with growth retardation and infections caused by pathogens, which do not usually cause disease in normal subjects, indicate the presence of an immune system deficiency.

Diagnosis of primary immunodeficiency

For an initial diagnosis of PID, the attending physician can perform two essential tests:

• a complete blood count which determines the number of blood cells and their characteristics;
• the calculation of serum immunoglobulins.

If serum immunoglobulins are absent or show values ​​below normal, a diagnosis of hypo/agammaglobulinemia is made. Serum immunoglobulin values ​​should be compared to those in normal subjects of the same age.

If the blood formula also shows a drop in circulating lymphocyte levels, we speak of a combined immune deficiency.

Other indicators should also be monitored:

History of the disease or anamnesis : a thorough family history is essential to identify a possible hereditary transmission. This involves investigating in relatives about diseases similar to that of the patient such as allergies, autoimmune diseases, tumors, possible reactions to vaccines, antibiotics and immunoglobulins or any previous surgery.

Physical examination : primary immunodeficiency can manifest as: pallor, general malaise, malnutrition, skin rashes, etc.

In T or B lymphocyte deficiencies, cervical lymph nodes and adenoid and tonsillar tissue are reduced or absent, chronic cough and decreased muscle mass may be present. Common symptoms include diarrhea, malabsorption, and growth failures.

To accurately identify the type of immunodeficiency, further immunological and molecular genetic testing may be required.

Treatment of primary immunodeficiency

In immune compromised patients with significant viral infections, antiviral drugs, such as amantadine or rimantadine for influenza, acyclovir for herpes infections, and ribavirin for respiratory syncytial virus, may be used.

The treatment of humoral immune deficiencies such as B lymphocyte deficiency is by administration of immunoglobulins. It is a substitution therapy, similar to that applied in people with type 1 diabetes, unable to produce insulin and where the administration of this hormone represents a replacement treatment.

This therapy based on the administration of immunoglobulins has proven its effectiveness in patients with PID and has considerably reduced mortality and morbidity. In many cases, it helps lead a healthy quality of life.

Current treatments administered both intravenously and subcutaneously appear to be effective. The choice of one product or another is determined according to the needs and requirements of each patient.

Complete correction of immunodeficiency requires stem cell or bone marrow transplantation. In patients with intact or only partially compromised cellular immunity, the use of immunosuppressants is necessary to prevent graft rejection.