[1] It is an X-linked recessive inheritance trait, stemming from a mutated (abnormal) version of the IL2RG gene located on the X-chromosome.

[4] This is followed by viral infections such as pneumonitis, an inflammation of the lung which produces common symptoms such as cough, fever, chills, and shortness of breath.

[6] This is likely due to passive immunity received from the mother in order to protect the baby from infections until the newborn is able to make their own antibodies.

In X-inactivation the preferential selection of the non-mutant X chromosome during development results in the outcome that none of the mature female cells actively express the X-SCID mutation, they are immunologically unaffected and have no carrier burden.

Since only 1/3 of all X-SCID patients have a positive family history of SCID, it is hypothesized that de novo mutations account for a significant percentage of cases.

[9] Interleukins are produced by lymphocytes, among other cell types, and are released in response to antigenic and non-antigenic stimuli.

The mutation can occur through large, or even single nucleotide, deletions in the IL2RG gene, that disable the common gamma chain so that it is unable to bind with other receptor subunits and signal cytokine activation.

[14] Alternatively, Amniocentesis, which entails extracting a sample of the fluid which surrounds the fetus, can be performed 15 to 20 weeks into gestation.

[17] Individuals who have the SCID phenotype will have TREC counts as low as <30, compared to approximately 1020 for a healthy infant.

Newborn screening of X-SCID based on TREC count in dried blood samples has recently been introduced in several states in the United States including California, Colorado, Connecticut, Delaware, Florida, Massachusetts, Michigan, Minnesota, Mississippi, New York, Texas, and Wisconsin.

[22] The former attempts to manage the opportunistic infections common to SCID patients[22] and the latter aims at reconstituting healthy T-lymphocyte function.

[23] From the late 60s to early 70s, physicians began using "bubbles", which were plastic enclosures used to house newborns suspected to have SCIDS, immediately after birth.

[24] The bubble, a form of isolation, was a sterile environment which meant the infant would avoid infections caused by common and lethal pathogens.

[26] Here, a catheter is inserted into the vein and a fluid, containing antibodies normally made by B-cells, is injected into the patient's body.

[27] Antibodies, Y-shaped proteins created by plasma cells, recognize and neutralize any pathogens in the body.

[23] Bone marrow transplantation (BMT) is a standard curative procedure and results in a full immune reconstitution, if the treatment is successful.

[30] Firstly, a bone marrow transplant requires a human leukocyte antigen (HLA) match between the donor and the recipient.

[34] The depletion of T-cells in the donor tissue and a close HLA match will reduce the chances of graft-versus-host disease occurring.

[37] In particular, the common lymphoid progenitor gives rise to the lymphocytes involved in the immune response (B-cell, T-cell, natural killer cell).

[35] In order to transfer a functional gene into the target cell, viral or non-viral vectors can be employed.

[31] If the appropriate treatment such as intravenous immunoglobulin supplements, medications for treating infections or a bone marrow transplant is not administered, then the prognosis is poor.

[38] For this reason, the diagnosis of X-linked SCID needs to be done early to prevent any pathogens from infecting the infant.

[44] In addition, if X-linked SCID is known to affect a child, then live vaccines should not be administered and this can save the infant's life.

Live attenuated vaccines, which consist of weakened pathogens inserted into the body to create an immune response, can lead to death in infants with X-linked SCID.

[46] The results of bone marrow transplant are most successful when the closest human leukocyte antigen match has been found.

[47] If a close match is not found, however, there is a chance of graft-versus-host-disease which means the donor bone marrow attacks the patient's body.