The immune system defends us from two arms against millions of microorganisms around it. The first of these is the non-specific natural immune response that starts immediately when the infectious agent enters the body, and the second is the acquired immune response that later develops specific to the pathogen.
Both arms perform their duties sequentially, ensuring that the host maintains a healthy life and gains resistance to infections. Neutrophils, the most important cell group of the innate immune system, lactoferrin, proteases and the complement system are in the first step of defense. Then, antigen-presenting cells reinforce the development of resistance by making antibodies by B lymphocytes after the antigen is presented to T lymphocytes.
Children tend to have more frequent infections. Young children's susceptibility to infections depends on many factors. Immune system development in children follows a maturation process, and serum IgG levels reach adult values after the age of 4-6 and IgA levels at the age of 10-12. For this reason, children are frequently infected in the first five years of life.
50% of children who are frequently sick are normal children. The most important reason why infections are common during this period is that it encounters infectious agents for the first time that it has not encountered before, and therefore the immune system is not yet fully mature.
There are some risk factors associated with frequent infections in children. These are passive smoking, allergies, gastroesophageal reflux, going to nursery or having a sibling who goes to school, anatomical problems of the respiratory tract, and unbalanced and malnutrition. The majority of frequently ill children are normal, healthy children. There is no underlying disease that causes these children to get sick frequently.
It is normal for children to get sick 6-8 times a year. If the child goes to nursery or has a sibling who goes to school, this number may increase to 10-12. The most common infections are respiratory tract infections and are mostly caused by viral causes. The growth and development of these children is normal, their infections are mild, and their response to treatment is good. Between infections, they are completely healthy.
30% of patients with recurrent infections are children with atopic disease. Allergic inflammation in atopic children Due to the chronic inflammation caused by the respiratory tract in the airways, microorganisms attach to the respiratory tract epithelium and an infection occurs. The differential diagnosis of allergic rhinitis, asthma-related sinusitis, asthma-related cough conditions and possible immunodeficiency should be made carefully. Recurrent otitis media is often caused by eustachian tube dysfunction secondary to atopy. These patients benefit greatly from tympanostomy.
10% of patients with recurrent infections are children with chronic diseases. These children have a typical chronic disease appearance and have growth retardation. They gain weight slowly. In patients, the function of the immune system is impaired due to systemic disease.
Diabetes, malignancies (leukemia, lymphoma, etc.), chronic renal failure, nephrotic syndrome, malabsorption, liver failure, sickle cell anemia, HIV infection, immunosuppressive treatment, radiotherapy and splenectomy can be counted among these.
10% of children who are frequently ill have primary (congenital) immunodeficiency. If the infections are more severe than expected, there is no full recovery with antibiotic treatments, prolonged antibiotic treatments are required and the disease becomes chronic, it becomes important to evaluate the immune system by suspecting immunodeficiency.
Situations in which immunodeficiency is suspected are listed below:
1- Four or more ear infections in a year
2- Two or more sinus infections in a year
3- Antibiotic use for two months or longer
4- Two or more pneumonias in a year
5- Growth and development retardation
6- Recurrent skin, deep tissue or organ abscesses
7- Long-lasting fungal infection in the mouth or on the skin
8- Need for intravenous antibiotic use to cure the infection
9- Two or more deep tissue-based infections, infection with opportunistic microorganisms
>10- Family history of immunodeficiency
Primary immunodeficiency diseases are a group of diseases that progress with chronic and/or recurrent bacterial, fungal, protozoal and viral infections.
The immune system is humoral, It consists of 4 main parts: cellular, phagocytic and complement system. with immunodeficiency 50-60% of the diseases are humoral immune system disorders, 10-15% are cellular immune system defects, 15-29% are combined immunodeficiencies, 10-15% are phagocytic system disorders and 1-3% are It causes complement system deficiencies.
In primary immune deficiencies, the age of onset varies depending on the type of immune deficiency. Infections in patients with severe combined immunodeficiency (both T and B cell disorders: SCID) occur on days 3-4. It starts before the month. In B cell disorders such as Bruton's agammaglobulinemia (X-linked agammaglobulinemia), clinical findings appear as maternal IgG levels decrease. Therefore, infections occur on days 7-9. It may not be observed for up to a month.
In the presence of signs and symptoms suggestive of a specific immune deficiency, the immune system should be evaluated. Additionally, patients who are recurrent, severe, do not respond well to treatment, or have complications or have a history of opportunistic infections should be carefully evaluated for immunodeficiency. An important point here is the development of fatal and widespread infections after live vaccines, especially after BCG vaccine.
Tests to be performed in patients with suspected immunodeficiency
The first examinations to be performed in immune deficiencies are complete blood count and immunoglobulins. With complete blood count, leukocyte count and its formula (lymphocyte, neutrophil and eosinophil), erythrocyte and platelet count are evaluated.
Immunoglobulin levels may be low to varying degrees in humoral and combined immunodeficiencies. Measurement of IgG subgroups and specific antibody response are also among the B cell evaluation tests. The response to protein antigens is generally impaired in IgG1 deficiency, and the response to polysaccharide antigens is impaired in IgG2 deficiency.
An absolute lymphocyte count < 3000mm3 in infancy and <2000mm3 in older children indicates a T lymphocyte defect.
Evaluation of T cell subgroups (CD4, CD8) using flow cytometry, absence of thymus on chest X-ray in the newborn suggests T cell disorder. The easiest way to evaluate the complement system is to measure CH50. Chronic granulomatous disease can be diagnosed by evaluating the neutrophil oxidative mechanism with the NBT (Nitroblue tetrazolium) test or dihydrorhodamine. Patients with delayed umbilical cord drop or In people with impaired healing, leukocytes are low in the wound area.
Leukocyte adhesion defect can be diagnosed by evaluating CD11/CD18 and sLex (CD150) adhesion molecules on neutrophils with flow cytometry. Serum alpha fetoprotein level in patients with ataxia telangiectasia is well above normal limits for age. The average platelet volume of my patients with Wiskott Aldrich syndrome is small and their platelet counts are low.
Primary immunodeficiencies are observed more frequently than expected in our country where consanguineous marriages are common. Diagnosing primary immunodeficiencies before serious infections occur is important in terms of prognosis and timely genetic counseling to the family.
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