Severe Combined Immunodeficiency

By | June 10, 2022

Severe Combined Immunodeficiency ( SCID ) is a collective term for severe congenital immunodeficiencies in which T lymphocytes are always absent. A SCID is always based on a gene mutation. If left untreated, this immune deficiency will inevitably lead to death.

What is Severe Combined Immunodeficiency?

The German translation for the English term Severe Combined Immunodeficiency is analogous to severe combined immunodeficiency. The Severe Combined Immunodeficiency or SCID summarizes several different hereditary immune disorders. The common feature of all diseases referred to under this term is the absence of T-lymphocytes. For hyperthecosis ovary in dictionary, please visit

Depending on the immune defect, B lymphocytes and natural killer cells (NK cells) may be missing or insufficient. The T lymphocytes control the cellular immune response. In the case of SCID, the defense against infected cells no longer takes place. At the same time, however, the antibody-related defense against antigens by the B lymphocytes or the function of the natural killer cells can also be impaired.

The immune deficiency begins shortly after birth and leads to severe and recurring infections with unusual pathogens. Infections that are normally harmless in people with a healthy immune system are very serious in these immunodeficiencies and are usually fatal if left untreated.

Severe combined immunodeficiency must be differentiated from acquired immunodeficiencies due to severe diseases or harmful environmental influences in order to determine the right treatment strategy. Overall, for every 100,000 newborns, one to two children are affected by SCID.


A SCID is always caused by a genetic defect. These are mostly autosomal recessive or x-linked changes. Based on the causes, the SCID can be classified into three forms. Severe combined immunodeficiency is triggered, among other things, by defects in cytokine receptor genes, antigen receptor genes or adenosine deaminase genes (ADA genes).

The corresponding cytokine receptors are receptors for the binding of interleukins. Interleukins are known to activate the immune response. If, on the other hand, antigen receptors are defective, the antigens cannot be bound to the cell surface, so that there is no cellular immune response. Finally, the ADA genes ensure the breakdown of purines.

If there is a genetic defect in one of the ADA genes, the purines accumulate in the body and are mostly converted into dATP (deoxyadenoside triphosphate). In turn, deoxyadenoside triphosphate inhibits an enzyme responsible for DNA synthesis. The reduced DNA synthesis prevents rapid formation of T-lymphocytes and other immune cells. Defects in the cytokine receptor genes play the most important role in SCID.

A mutation on an x-chromosomal gene is responsible for almost 50 percent of severe combined immunodeficiency. This gene codes for several interleukin receptors including the interleukin-2 receptor. Because of this mutation, precursors of T lymphocytes and NK cells can no longer be formed. In the case of the remaining mostly autosomal recessive hereditary gene defects, there are also changes in interleukin receptors, defects in antigen receptors and disorders of DNA synthesis.

Symptoms, Ailments & Signs

SCID usually becomes noticeable in infancy or early childhood. Only in very rare cases do the first symptoms appear later. There are even progressive forms that only begin in adulthood. For affected infants and children, failure to thrive is particularly typical, which manifests itself in growth and development delays.

Also characteristic are recurring and severe infections. Recurrent pneumonia is observed particularly frequently. But middle ear infections, bronchitis or fungal diseases also often occur.

Furthermore, diarrhea and indigestion occur constantly. Infections are usually very severe. As with other immune defects, the affected patients often contract infections with normally harmless germs, viruses or fungi.

Diagnosis & course of disease

SCID can be detected by determining the antigens on leukocytes. These antigens are fluorescently labeled and determined by immunophenotyping. If no or only a few antibodies are found, SCID can be assumed.

A small thymus, lymphopenia below 1500 cubic millimeters, missing lymph nodes and missing tonsils are also typical. In contrast to the lymphocytes, the number of granulocytes is usually normal. A lack of gamma globulins can be determined by means of electrophoresis. Vaccination failure also indicates SCID.

Before carrying out genetic tests, however, it is checked whether certain antibodies have been formed. The exact type of SCID can now be determined in the molecular genetic examination. Prenatal diagnosis is also possible for almost all SCID diseases.


Severe Combined Immunodeficiency leads to a number of different complaints and symptoms. As a rule, these already occur in childhood and have a very negative effect on the development of the child. Those affected suffer from severe delays in development and growth. This can often lead to bullying or teasing in children, which can be accompanied by psychological problems or mild depression.

Swallowing disorders can also become noticeable in the course of the severe combined immunodeficiency and have a negative effect on the child’s eating behavior. The affected children often suffer from inflammation in the lungs and also from chronic diarrhea. The patient’s quality of life is significantly reduced and limited by the disease.

There are no complications in the treatment of severe combined immunodeficiency. With the help of antibiotics and other medications, the infections and inflammations can usually be treated well. The developmental disorders are treated by a psychologist or by various therapies. However, it cannot be universally predicted whether this will lead to a complete cure. However, the patient’s life expectancy is usually not reduced or otherwise restricted.

When should you go to the doctor?

Severe combined immunodeficiency usually always requires medical examination and treatment. This disease cannot heal itself, since it is a congenital disease that can possibly be passed on to the descendants. If the person concerned wishes to have children, genetic counseling should be carried out to prevent the disease from being passed on to the descendants.

A doctor should be consulted for Severe Combined Immunodeficiency if the sufferer suffers from severe failure to thrive. This leads to severely delayed growth, with the development of the child generally being significantly restricted and reduced. The organs of those affected are also severely underdeveloped, so that various infections occur. If these symptoms occur, a doctor must be consulted. Furthermore, permanent diarrhea or severe digestive disorders can indicate severe combined immunodeficiency and should be treated by a doctor.

The diagnosis of Severe Combined Immunodeficiency can be made by a general practitioner, with the treatment itself being tailored to the exact symptoms. The life expectancy of the child may also be significantly reduced due to severe combined immunodeficiency.

Treatment & Therapy

A severe combined immunodeficiency must first be treated symptomatically. The main aim is to minimize the risk of infection. This is achieved, among other things, by the patients concerned having to live under sterile conditions. For example, they have to stay under a plastic tent at all times, which shields them from the outside world.

If infection occurs, immediate drug treatment is necessary. In the case of a bacterial infection, appropriate antibiotics are used. Fungal infections require the use of antifungals and viral infections of antivirals. However, these measures can only prolong life.

A real curative therapy is a transplantation of blood stem cells from suitable donors. Permanent healing is possible. However, it can also lead to health side effects due to the necessary chemotherapy. Direct gene therapies were also tried, which initially promised good results but later frequently triggered leukemia .


SCID cannot be prevented because it is a genetic disease. In the case of familial accumulation and the desire to have children, human genetic counseling is recommended to reduce the risk for the offspring.


The term ‘severe combined immunodeficiency’ covers various immune diseases or syndromes that affect the immune system. Such defects are usually hereditary and not acquired. The diagnosis is already made in childhood, common diseases due to the damaged immune system are among the most common features of SCID.

Both close-meshed therapy and strict follow-up care are necessary in order to largely counteract the immune deficiency. Without treatment, however, SCID can become life-threatening. There are the following methods of treatment: The drug variant, in which antibiotic or antiviral agents are administered in a combined form, or a stem cell donation. Both methods can be associated with significant side effects, and with stem cell donation there is also a risk of leukemia later on.

This development must be prevented as part of aftercare. Consistent care by a specialist is required in order to detect malignant changes in the blood in good time. Compatibility is checked when medication is administered. If side effects occur, the patient is prescribed alternative preparations. In the event of an unexpected deterioration, immediate medical attention or hospitalization is required. A life-threatening outcome must be prevented and the patient must be stabilized immediately. Even after your stay in the clinic, aftercare is continued by a specialist.

You can do that yourself

The Severe Combined Immunodeficiency means an extremely high risk of infection for the patient. In everyday life, those affected should therefore protect themselves as well as possible from infection.

In such cases, doctors recommend shielding yourself from other people, even if this is difficult to do in everyday life. The patients are relatively safe in an impermeable plastic tent, but social life is reduced to just a few contacts. Close ties with the family are all the more important. The parents of sick children should observe them closely in order to recognize any infections immediately. When the organism is infected, it needs rapid treatment with drugs. Discipline and loving attention are essential for a positive mood.

Life expectancy is quite low, especially without therapy. Regardless of the type of treatment, close proximity between parents and children is extremely important. She helps those affected through difficult times. If the disease has a history in the family, doctors recommend comprehensive human genetic counseling. The topics of the conversation relate on the one hand to the danger for the offspring and on the other hand to the possible options for reducing this risk.

Severe Combined Immunodeficiency