Name the disease that was first to get the gene therapy treatment. Write the cause of the disease and the effect it has on the patient.

Explanation

### Step-by-Step Solution:

1. **Identify the Disease**:
- The disease that was first treated with gene therapy is **Adenosine Deaminase Deficiency (ADA deficiency)**.

2. **Cause of the Disease**:
- The cause of ADA deficiency is the **deficiency of the enzyme Adenosine Deaminase (ADA)**. This enzyme is crucial for the metabolism of adenosine, which is important for the development of lymphocytes.

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