When Things Go Wrong by Bill Bryson

Author:Bill Bryson [Bryson, Bill]
Language: eng
Format: epub
Publisher: Knopf Doubleday Publishing Group
Published: 2020-04-21T00:00:00+00:00

III

IF WE DON’T die so much from communicable diseases anymore, plenty of other maladies have stepped in to fill the gap. Two types of diseases in particular are more visible now than they were in times past, in part at least because we aren’t being killed off by other things first.

One is genetic diseases. Twenty years ago, about five thousand genetic diseases were known. Today it is seven thousand. The number of genetic diseases is constant. What has changed is our ability to identify them. Sometimes one rogue gene can cause a breakdown, as with Huntington’s disease, which used to be known as Huntington’s chorea, from the Greek for “dance,” a strange and decidedly insensitive reference to the jerky movements of Huntington’s sufferers. It is a thoroughly wretched disease, affecting about one person in every ten thousand. Symptoms usually first appear when the victim is in his or her thirties or forties, and progress ineluctably to senility and premature death. It is all because of one mutation in the HTT gene, which produces a protein called huntingtin, one of the largest and most complex proteins in the human body, and we have no idea what huntingtin is for.

Far more often, multiple genes are at play, usually in ways too complex to fully understand. The number of genes that have been implicated in inflammatory bowel disease, for instance, is comfortably over a hundred. At least forty have been linked to type 2 diabetes, and that is before you start to factor in other determinants like health and lifestyle. Most diseases have a complex array of triggers.

That means that it is often impossible to pinpoint a cause. Take multiple sclerosis, a disease of the central nervous system in which sufferers experience a gradual onset of paralysis and loss of motor control, nearly always beginning before the age of forty. It is indubitably genetic, but it also has a geographical element that no one can quite explain. People from northern Europe get it much more often than people from warmer climes. As David Bainbridge has observed, “Why a temperate climate should make you attack your own spinal cord is not so obvious. Yet the effect is clear, and it has even been shown that if you are a northerner you can reduce your risk by relocating southward before puberty.” It also affects women disproportionately, again for no reason that anyone has yet determined.

Mercifully, most genetic diseases are quite rare, often vanishingly so. One of the more famous sufferers of a rare genetic disorder was the artist Henri de Toulouse-Lautrec, who is thought to have suffered from pycnodysostosis. Toulouse-Lautrec was normally proportioned until puberty, but then his legs stopped growing while his trunk continued growing to normal adult size. In consequence, when standing, he looked as if he were on his knees. Only about two hundred cases of the disorder have ever been recorded.

Rare diseases are defined as diseases that afflict no more than one person in two thousand, and there is a paradox

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