Since I mentioned the NIH in the context of the Molecular Libraries business, I wanted to bring up something else that a reader sent along to me. There's a persistent figure that's floated whenever the agency talks about translational medicine: 4500 diseases. Here's an example:
Therapeutic development is a costly, complex and time-consuming process. In recent years, researchers have succeeded in identifying the causes of more than 4,500 diseases. But it has proven difficult to turn such knowledge into new therapies; effective treatments exist for only about 250 of these conditions.
It shows up again in this paper, just out, and elsewhere. But is it true?
Do we really know the causes of 4,500 diseases? Outside of different cancer cellular types and various infectious agents, are there even 4,500 diseases, total? And if not, how many are there, anyway, then? I ask because that figure seems rather high. There are a lot of single-point-mutation genetic disorders to which we can pretty confidently assign a cause, but some of them (cystic fibrosis, for example) are considered one disease even though they can be arrived at through a variety of mutations. Beyond that, do we really know the absolute molecular-level cause of, say, type II diabetes? (We know a lot of very strong candidates, but the interplay between them, now, there's the rub). Alzheimer's? Arthritis? Osteoporosis? Even in the cases where we have a good knowledge of what the proximate cause of the trouble is (thyroid insufficiency, say, or Type I diabetes), do we really know what brought on that state, or how to prevent it? Sometimes, but not very often, is my impression. So where does this figure come from?
The best guess is here, GeneMap. But read the fine print: "Phenotypes include single-gene mendelian disorders, traits, some susceptibilities to complex disease . . . and some somatic cell genetic disease. . ." My guess is that a lot of what's under that banner does not rise to "knowing the cause", but I'd welcome being corrected on that point.