ADA deficiency causes Severe Combined Immunodeficiency (SCID).

Enzyme replacement therapy is only a temporary treatment.

Gene therapy using genetically engineered lymphocytes is also temporary because lymphocytes have a limited lifespan and require repeated infusions.

Bone marrow transplantation can be effective but is not the gene-therapy-based permanent cure discussed in NCERT.

If the functional ADA gene is introduced into cells at an early embryonic stage, the gene becomes part of the developing body's cells and can provide a permanent cure.

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