Mrs. Jones and Mrs. Smith, who have the identical medical conditions, are treated with the same medication. However, Mrs. Jones gets better but Mrs. Smith does not respond to the treatment. Why does this happen?

Mrs. Jones and Mrs. Smith, who have the identical medical conditions, are treated with the same medication. However, Mrs. Jones gets better but Mrs. Smith does not respond to the treatment. Why does this happen?


There are a variety of reasons, but the one that has recently been getting a great deal of attention relates to the role that genetic factors play.


Changes or variations in genes, or mutations, can be the reason why certain medications are effective or ineffective in different individuals. For example, gene mutations can cause a decrease or an increase in the absorption of a drug into the body. Decreased absorption can result in an insufficient amount of the medication, making it less effective.


In contrast, an increase in the absorption of the drug can cause an excessive amount, resulting in toxic symptoms.


A mutation in a gene can also cause an increase or decrease in the metabolism or breakdown of the drug. An excessive breakdown results in a decreased amount of the medication being available to be effective. Or the gene variation can be responsible for decreased drug metabolism, resulting in too much medication.


That's the bad news. The good news is that something can be done to help correct or improve this situation.


Research is now underway to not only find ways to identify the presence of such gene mutations but also how to correct them. For example, if it is determined that a person has a gene mutation that causes a specific antibiotic to be ineffectual, then a more effective antibiotic can be chosen to treat the person's infection.


The same can be done with other types of medications. The result will be that patients will have tailor-made treatment plans that apply only to them.


Genetic advances have also been helpful in the treatment of certain types of cancer. The body contains genes called “tumor suppressors,” and their role is to suppress the growth of cancers. A mutation in one of the suppressor genes can make the gene ineffectual in suppressing the cancer growth, and the tumor will grow and spread.


If, however, a similar DNA suppressor gene can be introduced into the body to replace the mutated one, then this gene will stop the excessive cancer growth.


These are just a few examples of how advances in genetics will drastically change the way diseases will be treated. And these advances are not that far away. In fact, some of them are already being used.


Dr. Murray Feingold is the physician in chief of The Feingold Center for Children in Massachusetts, medical editor of WBZ-TV and WBZ radio, and president of the Genesis Fund. The Genesis Fund is a nonprofit organization that funds the care of children born with birth defects, mental retardation and genetic diseases.