Health Problems, Small Genetic Differences

When you get right down to it—and by "right down to it," I mean at the DNA level—we are far more like one another than most of us would care to admit. It is estimated that we are 99 percent genetically identical, with that varying 1 percent causing quite a lot of variance. (The 1 percent explains, for instance, why I'm writing this column instead of sprinting in the Olympics or starring as the next James Bond.) An ever-growing body of research is also demonstrating how some of these differences put us at risk for a variety of diseases, including cancer, Alzheimer’s, and disorders that affect the immune system. Many of these differences are as small as one can imagine: a single change in the order of our DNA.
As I learned in college, and children now learn in elementary school, DNA is made up of four letters, or nucleotides: adenosine (A), guanine (G), cytosine (C), and thymidine (T). At certain points in our genes, we have variations in these letters, called polymorphisms. For example, where one part of the population may have a C, the rest of the population will have a T. These single nucleotide polymorphisms are known in the field as SNPs (pronounced "snips").







In a recent paper in the New England Journal of Medicine, a group of investigators looked at SNPs from over 2,500 patients with two rheumatologic disorders—lupus and rheumatoid arthritis—and compared their DNA with that of over 2,000 normal patients. The scientists concentrated their efforts on 13 different genes on a part of chromosome 2 that had previously been identified as containing genes related to these disorders. Patients with a particular SNP in a gene called STAT4 were 32 percent more likely to have rheumatoid arthritis and 55 percent more likely to have lupus. If you had two copies of this particular SNP (one from each of your parents), then your risk for either disorder was even higher.

Transmitted Infections

There’s been a lot of talk recently about being contagious. But what does "contagious" really mean and what’s the responsibility that goes along with being contagious? There are some people who wade fearlessly into a room full of sneezing, coughing, snotty children and others who use antibacterial lotion after any contact with solid matter.

Back in the day, when a child in the neighborhood came down with chicken pox, all of his friends were sent to visit. Our moms knew that getting chicken pox as a child was a better deal than getting it as an adult.
At the other extreme is Ebola virus—highly contagious and frequently lethal. No one will be dropping by to pick this up. Putting yourself at risk for Ebola would border on lunacy, and exposing someone to Ebola would be reprehensible.

Somewhere in between falls Andrew Speaker—the lawyer from Atlanta who flew to his wedding on commercial flights despite having tuberculosis—a man who’s had more than his 15 minutes of fame (or infamy).

I’m still not sure what upsets people most about this. Was it that he had drug-resistant TB? If so, does that mean that we’d all be OK sharing row 16 with someone who had regular TB? Was it that he was putting hundreds, if not thousands, of people at risk with his careless globetrotting? Well, in real life people don’t get TB from a handshake or a shared bathroom.

TB is spread by coughing and sneezing, and then only by people with relatively advanced disease. Media reports indicate that Speaker was neither coughing nor sneezing and his disease was not advanced.
What bothers me most about this incident is our protagonist’s willingness to put others at risk (albeit a small one) when he probably knew, at some level, it wasn’t the right thing to do. It’s easy to do the right thing when it’s easy. It’s harder to tell your fiancée that you’re getting married at the Elvis chapel, instead of in Europe, because you’re just not sure how contagious you are.