Final answer:
Gene therapy is primarily focused on diseases caused by single-gene defects like cystic fibrosis and hemophilia. The approach has seen some success, including in treating ADA deficiency, but comes with serious risks such as inflammatory responses and potential for causing cancer. While still experimental and fraught with ethical considerations, gene therapy holds promise for future medical advancements.
Step-by-step explanation:
Gene Therapy and Diseases Targeted
In gene therapy, diseases caused by single-gene defects are often the initial focus for treatment. Conditions such as cystic fibrosis, hemophilia, muscular dystrophy, and sickle cell anemia are typically prioritized because they result from the malfunction of a single gene, and thus are theoretically easier to treat with gene therapy techniques. One well-known application of gene therapy was on a young girl with adenosine deaminase deficiency (ADA deficiency), which disrupts her immune system due to the lack of ADA enzyme. In her treatment, bone marrow stem cells were extracted, genetically modified to include the missing gene, and returned to her body, resulting in a restoration of her immune functions, necessitating repeated treatments for sustained results.
However, challenges persist in gene therapy implementation, as scientists navigate complications like inflammatory responses to the viral vectors used, such as adenovirus, and the risk of inadvertently causing other health issues like cancer. The tragic case of Jesse Gelsinger illustrates the potential dangers of gene therapy, where an immune response to the adenovirus vector used for treating ornithine transcarbamylase deficiency (OTC) led to his death. While no gene therapies are currently marketed in the United States, advancements, especially those targeting the p53 gene involved in many cancers, suggest that gene therapy treatments may be more common in the future, despite the ethical implications and risks involved.