Syndrome X patients do not develop physically in childhood, and thus appear to not be aging. However this is an extreme malfunction of developmental programs, not an absence of aging. The operation of their metabolism still generates all of the forms of damage that lead to degenerative aging, but these individuals die young and so none of that is given the chance to rise to the level of displaying the recognizable symptoms of aging.
Some people persist in trying to make the link that doesn't exist, however. This popular science article is a decent coverage of what is presently called Syndrome X and present thoughts on theories of aging. The researcher whose work on Syndrome X is mentioned here has adopted a variant view of aging as a genetic program, and seeks to sequence the few known Syndrome X patients in search of the common genetic cause in the hopes that this will inform considerations of normal aging. I, among others, think that this is a futile quest, though it may produce the path to curing Syndrome X in the future, should it turn out to have a simple root cause in genetic mutation.
Richard Walker has been trying to conquer ageing since he was a 26-year-old free-loving hippie. Walker, now 74, believes that the key to ending ageing may lie in a rare disease that doesn't even have a real name, "Syndrome X". He has identified four girls with this condition, marked by what seems to be a permanent state of infancy, a dramatic developmental arrest. He suspects that the disease is caused by a glitch somewhere in the girls' DNA.
Most scientists say that ageing is not caused by any one culprit but by the breakdown of many systems at once. Our sturdy DNA mechanics become less effective with age, meaning that our genetic code sees a gradual increase in mutations. Telomeres, the sequences of DNA that act as protective caps on the ends of our chromosomes, get shorter every year. Epigenetic messages, which help turn genes on and off, get corrupted with time. Heat shock proteins run down, leading to tangled protein clumps that muck up the smooth workings of a cell. Faced with all of this damage, our cells try to adjust by changing the way they metabolise nutrients and store energy. To ward off cancer, they even know how to shut themselves down. But eventually cells stop dividing and stop communicating with each other, triggering the decline we see from the outside.
Scientists trying to slow the ageing process tend to focus on one of these interconnected pathways at a time. Some researchers have shown, for example, that mice on restricted-calorie diets live longer than normal. Other labs have reported that giving mice rapamycin, a drug that targets an important cell-growth pathway, boosts their lifespan. Still other groups are investigating substances that restore telomeres, DNA repair enzymes and heat shock proteins.
During his thought experiments, Walker wondered whether all of these scientists were fixating on the wrong thing. What if all of these various types of cellular damages were the consequences of ageing, but not the root cause of it? He came up with an alternative theory: that ageing is the unavoidable fallout of our development.
Most researchers agree that finding out the genes behind Syndrome X is a worthwhile scientific endeavour, as these genes will no doubt be relevant to our understanding of development. They're far less convinced, though, that the girls' condition has anything to do with ageing. "It's a tenuous interpretation to think that this is going to be relevant to ageing," says David Gems, a geneticist at University College London.