Who was the first patient who was given gene therapy? Why was the given treatment recurrent in nature?

(A) The first patient to receive gene therapy was a $4$-year-old girl named Ashanti DeSilva.
She was suffering from Adenosine Deaminase $(ADA)$ deficiency.
This enzyme is crucial for the proper functioning of the immune system.
The disorder is caused by the deletion of the gene responsible for producing Adenosine Deaminase.
In some children,$ADA$ deficiency can be cured by bone marrow transplantation; in others,it can be treated by enzyme replacement therapy,where functional $ADA$ is administered via injection.
However,both these approaches are not completely curative.
As a first step towards gene therapy,lymphocytes from the patient's blood are grown in a culture outside the body.
$A$ functional $ADA$ $cDNA$ (using a retroviral vector) is then introduced into these lymphocytes,which are subsequently returned to the patient.
Since these cells are not immortal,the patient requires periodic infusion of such genetically engineered lymphocytes.
If the gene isolated from marrow cells producing $ADA$ is introduced into cells at early embryonic stages,it could provide a permanent cure.
Process flow:
$1$. Through cloning,several $ADA$ gene copies are produced.
$2$. The viral genes are replaced by $ADA$ genes in the modified retrovirus.
$3$. From the bone marrow of the patient,lymphocytes are obtained and cultured in vitro.
$4$. These lymphocytes are infected by recombinant retroviruses.
$5$. $ADA$ gene is expressed in these infected lymphocytes.
$6$. Infected lymphocytes are injected back into the patient's body.
$7$. $ADA$ gene is expressed,and the deficiency is partially corrected.