SCID patients are usually affected by severe bacterial, viral, or fungal infections early in life and often present with interstitial lung disease, chronic diarrhea, and failure to thrive.

[3] Ear infections, recurrent Pneumocystis jirovecii (previously carinii) pneumonia, and profuse oral candidiasis commonly occur.

These babies, if untreated, usually die within one year due to severe, recurrent infections unless they have undergone successful hematopoietic stem cell transplantation or gene therapy in clinical trials.

Several symptoms may indicate a possibility of SCID in a child, such as a family history of infant death, chronic coughs, hyperinflated lungs, and persistent infections.

Clinical diagnosis based on genetic defects is also a possible diagnostic procedure that has been implemented in the UK.

The delay in detection is because newborns carry their mothers' antibodies for the first few weeks of life and SCID babies look normal.

All states in the U.S.[14] are performing screening for SCID in newborns using real-time quantitative PCR to measure the concentration of T-cell receptor excision circles.

The first reported case of successful transplant was a Spanish child patient who was interned in Memorial Sloan Kettering Cancer Center in 1982, in New York City.

Physicians have also had some success with in utero transplants done before the child is born and also by using cord blood which is rich in stem cells.

In utero transplants allow for the fetus to develop a functional immune system in the sterile environment of the uterus;[17] however complications such as GVHD would be difficult to detect or treat if they were to occur.

From the treatments of Ashanthi DeSilva in 1990, which is considered gene therapy's first success until 2014, around 60 patients were treated for either ADA-SCID or X-SCID[22] using retroviruses vectors.

SCID mice also serve as a useful animal model in the study of the human immune system and its interactions with disease, infections, and cancer.

These mice then receive bone marrow transplantation from SCID donors, allowing engraftment of human peripheral blood mononuclear cells (PBMC) to occur.

The condition remains a fatal disease, as the horse inevitably succumbs to an opportunistic infection within the first four to six months of life.