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Susceptibility to infection: signs, causes

by Josephine Andrews
Published: Last Updated on 432 views

Constantly ill – is that still normal or a sign of a weak immune system and thus an increased susceptibility to infections ? Here you can find out which symptoms indicate an immune deficiency and what treatment options are available for this. But not only illnesses cause a weakened immune system, also certain medications and therapies as well as age, pregnancy and an unhealthy lifestyle.

What does “morbidly susceptible to infection” mean?

Physicians distinguish between physiological and pathological (morbid) susceptibility to infection:

Physiological susceptibility to infection

Babies are born with an immature immune system . The immune system first has to get to know the germs in the environment and develop strategies to fight them – immunity against the pathogen in question develops. It is therefore completely normal if babies and small children, for example, always feel like they have a cold – or at least much more often than adults. For example, children up to school age experience eight to twelve mild infectious diseases a year, after which they fall ill less frequently.

The immune system of adults also has to deal with pathogens with which it has not had any contact before. That’s why everyone catches a cold, athlete’s foot or gastrointestinal infection at some point during the year.

Experts speak of a physiological susceptibility to infection . In most cases, the immune system gains the upper hand and successfully fights the infectious agent.

Pathological susceptibility to infection

But there are also people who are more sensitive to infectious agents and are therefore very often or almost constantly ill. In addition, infectious diseases can take a different and often more severe course in them. Experts refer to this as a pathological or morbid susceptibility to infection . This is usually due to an immune deficiency. This means that the body’s immune response to a pathogen or to the body’s own degenerated cells is inadequate. However, some immune defects can also lead to excessive immune reactions against foreign or endogenous substances.

Experts distinguish congenital and acquired immunodeficiencies:

  • congenital (primary) immunodeficiency : They are inherited from the parents. However, in half of those affected, congenital immune deficiencies only become apparent in adulthood, at over 25 years of age.
  • Acquired (secondary) immunodeficiency : Such an immune deficiency disease only arises again in the course of life.

Congenital immunodeficiencies

Scientists now know of almost 300 different primary immune defects. All are rare diseases.

Depending on the type of congenital immunodeficiency, different parts of the immune system are not fully functional. The development or maturation of immune cells, but also the formation of antibodies against pathogens, can be disrupted. If both immune cells and antibodies are affected, the term “combined” is used. An example of this is severe combined immunodeficiency (SCID) . Affected children get serious infectious diseases in infancy and die before the age of two if they are not treated in time.

In contrast, the combined immunodeficiency (CID) progresses more easily, since parts of the immune system are still functioning and continue to protect the body against infections as well as possible. People with CID can therefore be relatively healthy. The disease is sometimes not recognized until adulthood.

The term variable immunodeficiency syndrome (common variable immunodeficiency, CVID) includes various congenital immunodeficiencies in which the defense with immune cells works, but far too few or no antibodies are available to fight off infection. Those affected are therefore much more susceptible to infections than healthy people. CVID is relatively common for congenital immunodeficiency. The first symptoms can appear in early childhood, but often not until the third or fourth decade of life.

Warning signs of congenital immunodeficiency

It is not easy to differentiate between a pathological and a normal susceptibility to infection. It is not possible to say in general how many infections, what kind of infections and what course of the diseases can be considered normal. How often a person is ill is influenced, among other things, by living conditions such as the size of the family or attendance at a day-care center.

The range of symptoms for congenital immune defects is also large – the type and severity of the symptoms can vary from person to person.

Scientists have therefore considered other parameters that are typical of pathological susceptibility to infection:

Unusual infectious diseases

“Normal” germs, which only trigger mild infectious diseases in people with a healthy immune system, can lead to dangerous diseases in children or adults with a congenital immune deficiency. Chickenpox, rubella, herpes infections or fungal diseases (e.g. diaper thrush) that are otherwise relatively uncomplicated can suddenly become life-threatening in children.

In addition, there are pathogens that normally only rarely trigger a disease, such as Pneumocystis jirovecii, Aspergillus, cytomegaloviruses or cryptosporidia. However, people who have a pathologically weakened immune system develop severe liver diseases, pneumonia or diarrhea after infection with such an otherwise harmless germ.

Ill more often, more severely and for longer

Children or adults with a pathologically weakened immune system often become ill . They develop bacterial infections of the respiratory tract such as middle ear infections, sinus infections or bronchitis more frequently than healthy people. However, long-lasting diarrheal diseases are also typical, which can be accompanied by weight loss in adults and a small increase in weight and slowed growth in children. The infectious diseases are more severe and/or often affect organs that are not typically affected by the disease in question.

It usually takes those affected longer to recover . In addition, they are less responsive to normally effective drugs such as antibiotics, requiring repeated or prolonged treatment .

In people with a pathologically weakened immune system, complications are more likely to occur after vaccination with weakened pathogens ( live vaccination ).

Misguided Defense

A misguided immune system that acts against harmless substances or even against your own body is out of balance and can only regulate itself with difficulty. Doctors call this a disorder of immune regulation . It speaks for a congenital immunodeficiency.

An example: If the body forms antibodies against its own blood cells, there are far too few blood cells available – called autoimmune cytopenia. Possible signs of this are pale skin, headaches and reduced performance due to anemia. The lack of platelets (thrombopenia) disrupts blood clotting . The lack of white blood cells ( leukopenia ) makes the weakened immune system more susceptible to infections.

In some patients, the lymph nodes, spleen, or liver become swollen. The misguided defense can also be directed against the skin, joints, eyes or thyroid glands. This can lead to inflammatory diseases such as rheumatoid arthritis . Other possible consequences are a skin rash that is difficult to treat (eczema), chronic intestinal inflammation, unclear and recurring fever episodes and the formation of tissue nodules (granulomas) in the skin or in internal organs.

Increased risk of cancer

The cancer risk of patients with a congenital immunodeficiency is increased. Malignant tumors of the lymphatic system (lymphomas) often form. Cancers caused by viruses , such as soft tissue tumors associated with the Epstein-Barr virus or Kaposi’s sarcoma associated with the human herpes virus type 8, can also indicate a primary immune deficiency.

developmental disabilities

The many serious infections can delay the development of children with congenital immunodeficiency. The little ones grow more slowly (failure to thrive). Some of them even have an intellectual disability.

Diagnosis of congenital immunodeficiencies

The earlier a congenital immune deficiency is detected, the better it can be treated. Therefore, since August 2019, all newborns in Germany have been tested for SCID ( newborn screening ). There is no large-scale screening for all other primary immunodeficiencies – doctors and patients have to pay attention to warning signs themselves.

Since these are congenital, i.e. inherited diseases, an immune deficiency in close relatives can already indicate a disease in you or your child.

If you discover one or more warning signs in yourself or your child, you should have yourself or your child examined for a primary immunodeficiency!

blood count , a blood smear or the determination of antibodies can already bring clarity. If further steps are necessary, you should have yourself or your child referred to a center that specializes in immunodeficiency. You can find out where there are such centers on the Internet, for example at https://www.find-id.net/behandeln .

In a specialized therapy center, further examinations are carried out as required , such as:

  • Removal and analysis of a skin tissue sample (skin biopsy)
  • Removal and analysis of tissue from lymph nodes, intestinal mucosa or bone marrow
  • imaging methods such as x-rays and ultrasound
  • Urine and stool tests
  • Lung endoscopy ( bronchoscopy )
  • Colonoscopy _

Treatment of congenital immunodeficiencies

First, doctors try to treat existing infections. In addition, new infections should be prevented as far as possible. The affected children or adults receive preventive medication against bacteria, viruses and fungi.

Vaccinations are usually not useful in patients with a combined immune deficiency. It is best to discuss vaccinations with your doctor. It is important that the healthy family members have full vaccination protection in order to protect the affected person!

If the body lacks certain antibodies, these can be replaced with regular antibody infusions. Then the body can better defend itself against infections.

However, if the body acts against itself, i.e. if the immune regulation is disturbed (e.g. in the case of eczema, diarrhea, enlarged spleen or autoimmunity), the immune system must be slowed down. For this, the patients are given so-called immunosuppressants (e.g. cortisone) or drugs that kill dysregulated immune cells (e.g. the antibody rituximab). Sometimes the effect of these drugs is not sufficient – for example when the body’s own antibodies attack blood cells such as platelets to an extreme degree (severe autoimmune cytopenia) and the spleen is therefore greatly enlarged. It may then be necessary to remove the spleen and take antibiotics for life.

Healed by bone marrow transplantation

The only way to cure congenital immunodeficiency is to replace the diseased immune system with a bone marrow transplant from a healthy donor. However, this is not possible for all those affected and can be associated with serious complications. A team of specialists decides together with the patient whether a bone marrow transplant is an option in an individual case. Such a therapy should only be carried out in a specialized center!

Researchers are currently testing other treatment options such as gene therapy, in which modified genes in the patient’s stem cells are replaced with functional ones.

Acquired immunodeficiencies

A weakness of the immune system does not have to be congenital, but can also develop as a result of external influences. The cause of the most common acquired immunodeficiency disease AIDS (Acquired Immunodeficiency Syndrome) is infection with human immunodeficiency viruses ( HIV ). These weaken the immune system of the infected person so much that the body cannot even protect itself from actually harmless pathogens. Cancer cells also have an easier time – the cancer risk of those affected is therefore increased.

HIV is usually transmitted through unprotected sexual intercourse ( condoms protect against this!). In addition, HIV-infected pregnant women can pass the virus on to their child during childbirth .

The immune system is not only restricted in the case of AIDS, but also in the case of many other (chronic) diseases , for example in the case of:

Even after the spleen has been removed (splenectomy), there is an increased susceptibility to infection, at least for certain infectious agents: the immune system can no longer defend itself so well against bacteria with a capsule on the outside, such as pneumococci (Streptococcus pneumoniae). They can cause pneumonia, middle ear and sinus infections, among other things.

In addition, certain medications or therapies impair the immune system. Although radiation therapy fights cancer cells, it can also damage immune cells if the blood-forming bone marrow is also irradiated. In addition, certain drugs against cancer (cytostatics) inhibit the division of cells in the context of chemotherapy and thus also prevent the formation of new immune cells in the bone marrow.

Treatment with immunosuppressants may be necessary for severe inflammatory diseases and autoimmune diseases. These are active ingredients that suppress the immune system (e.g. cortisone, various rheumatism drugs ). Patients after an organ transplant also have to suppress their immune system with such drugs throughout their lives so that the body does not reject the implanted foreign organ. This makes the body more susceptible to infection.

Other causes of susceptibility to infection

In addition to immune defects, various diseases, infections and medication, other factors also influence the immune system. The following lifestyle factors, for example, have a negative effect :

  • persistent stress
  • consumption of alcohol and nicotine
  • Malnutrition (as in anorexia) or one-sided nutrition
  • overweight
  • lack of sleep
  • mental stress
  • physical overload, but also lack of exercise

Such factors can weaken the immune system and increase susceptibility to infections. Those affected catch an infection more quickly, complaining, for example, that they constantly have a cold. However, all of these factors can be prevented with a healthy lifestyle – in contrast to a pathological immune deficiency .

In addition, the ability of the immune system to protect the body from pathogens decreases with age . Among other things, less functional immune cells circulate in the blood. Older people are therefore more susceptible to infections and often develop more severe symptoms than younger patients. In addition, the immune system in older people can no longer distinguish between the body’s own and foreign structures. This increases the risk of autoimmune diseases, in which the body fights against its own components (such as rheumatoid arthritis).

Pregnant women are also more susceptible to infections, such as the flu virus. Because during pregnancy, the immune system adapts to the new situation, among other things in order not to reject the fetus. It is therefore particularly important for pregnant women to live a healthy life.

Although pregnant women are more susceptible to infections, their altered immune system also has a positive effect on the woman’s existing autoimmune diseases (e.g. multiple sclerosis).

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