People with SCID due to ADA deficiency are unable to fight off most types of infections, including bacterial, viral and fungal infections. ... Currently, the most effective treatment is transplantation of blood-forming stem cells from the bone marrow of a healthy brother or sister of the person with ADA deficiency.

As we know ADA deficiency leads to many immunological complications..
This can be treated by Bone Marrow Transplantation,
Injection of ADA Enzyme, Introduction of Lymphocytes with ADA ..
But all these are temporary treatments which just help in overcoming severe difficulties..
But by replacing the non functional ADA gene in the embryo with a functional ADA gene it will be a permanant cure...

Challenges of Bone Marrow Transplantation in ADA Deficiency
ADA deficiency is a genetic disorder that results in a lack of the enzyme adenosine deaminase, leading to a compromised immune system. Bone marrow transplantation is a common treatment for genetic disorders like ADA deficiency, but it poses challenges in effectively curing the disease.

Immunological Challenges
- In ADA deficiency, the immune system is severely compromised, making the patient susceptible to infections. This weakened immune system can complicate the success of a bone marrow transplant.
- The recipient's immune system may reject the transplanted bone marrow, leading to graft-versus-host disease, a potentially life-threatening complication.

Limited Success Rate
- Bone marrow transplantation for ADA deficiency has shown limited success rates in clinical trials. The efficacy of the treatment may vary depending on the patient's condition and overall health.
- The success of a bone marrow transplant in ADA deficiency is also influenced by the availability of a suitable donor, as finding a matching donor can be challenging.

Alternative Treatments
- Due to the limitations and risks associated with bone marrow transplantation, alternative treatments have been explored for ADA deficiency. Gene therapy is one such approach that aims to replace the defective ADA gene with a functional one.
- Gene therapy for ADA deficiency has shown promising results in clinical trials, offering a potentially more effective and safer treatment option compared to bone marrow transplantation.
In conclusion, while bone marrow transplantation remains a viable treatment option for ADA deficiency, it presents challenges related to immunological complications, limited success rates, and availability of suitable donors. Gene therapy emerges as a promising alternative with the potential to provide a more effective and safer cure for ADA deficiency.