Saturday 29 November 2014

Charcot Marie Tooth

You notice something new about yourself, or you wake up feeling crap for the seventh morning in a row and you go to see your doctor.  If s/he's any good and over the age of 30, s/he'll have seen a lot of sick people: 10 or 15 an hour for days on end since last Christmas and beyond. Each patient has been sick in their own special way but some have been sick with similar symptoms. Alert medicos ask if there might be an identical underlying cause to the same disease in each of several different persons.  If nobody has noticed the connexion before, the doctor gets to write up a hypothesis about cause and effect and often the disease becomes an eponym named after the discoverer.  Why just the other day I was talking about the causes of Down Syndrome. Sometimes the discovery doesn't get to be associated with the chap who makes it: neither William McBride nor Widikund Lenz got to name the developmental tragedy caused by the drug thalidomide. Some of these syndromes have such evocative names that you have to find out more, not only about the causes and symptoms, but also about the combination of events that perked someone up with "That's curious, I've seen that, or read about it, before".  One of those is Charcot-Marie-Tooth disease aka CMT which is a curious grab-bag of neuropathies that was first noticed by Jean-Martin Chacot and his assistant Pierre Marie in their paper "Sur une forme particulière d'atrophie musculaire progressive, souvent familiale débutant par les pieds et les jambes et atteignant plus tard les mains".  Coincidentally in the same year 1886 across the Channel an English neurologist Howard Henry Tooth was publishing his MD thesis on the same disease, describing particulière d'atrophie musculaire as a progressive muscular atrophy.

CMT is so diverse in its causes and symptoms that it is a bit like 'cancer' which only the most superficial assessment could call _a_ disease.  CMT is degenerative in that those with the wrong combination of genes start off fine and, as they turn into adults, start to decline from the outside in.  Initial symptoms include 'dropped foot', hammer-toes, and muscle-wasting in the lower leg.  Weakness and loss of feeling in the legs then starts to manifest in the hands and forearms and the doctor can put a label CMT on the condition. That's about all s/he can do because currently the disease is incurable. In times past, they would have lumped it in with muscular dystrophy; and quite possibly some doctors (less down with the medical hood) are still doing that. Which leads to the small-world observation that Charcot studied under the great French neurologist Guillaume-Benjamin-Amand Duchenne de Boulogne after whom Duchenne Muscular Dystrophy DMD is named. It is common enough in adults at 1:2500 but defects in many different genes can trigger symptoms, and many of these oddities are exceedingly rare.  70% of cases are caused by a duplication of part of chromosome 17 which puts the gene PMP22 out of whack, but about 40 other genes are known to be involved.  It shows just how complex and interconnected normal development and neuro-muscular control is.  Each of these 40 genes has to be switched on within a narrow range of tolerance for you and me to walk normally and yell out when we stub our toes.

Charcot stood astride (1825-1893) late 19th century medicine in a quite monumental way.  He held court in the Pitié-Salpêtrière Hospital in Paris and lots of younger giants were educated and inspired by him, including Sigmund "It's a cigar" Freud; Joseph "Reflex" Babinski [R]; William "Free Willy" James; Alfred "IQ test" Binet; Georges Gilles "fuckit-fuckit-fuckit" de la Tourette. I mentioned Charcot last year, partly because it was his birthday (as it is again today) but mainly because I was on about another of his students Theodor Escherich who makes the spelling of eponymous E. coli scho damned difficult for anglophones.

I was going to get round to tribbing Charcot in due course but CMT surfaced in my corner of the blogosphere just two days ago in a remarkable long-form article about a workaday athlete call Kim Goodsell.  Goodsell could have been a doctor like her brother, but she dropped out of medical school and lived the free life of a rover in the wilderness, coming back to civilisation periodically to make a bit of entrepreneurial money to feed her running-in-the-outback habit. In her 40s, her feet stopped working to command and she picked up a diagnosis of CMT.  Strangely, she had earlier been diagnosed with a heart arrhythmia which would have stopped the fell-running gallop of a less determined person. She couldn't believe that she had been dealt two crap cards from the deck of life and flung herself into an amateur research project to find the roots of her condition(s).  It was a long time since she'd been in medical school and she's forgotten all the jargon and in the interim new dictionaries of terms and techniques had been invented.  She needed to get her head round all this information and integrate it. Her journey through the darker reaches of PubMed in search of enlightenment was a bit like Simone George applying her lawyerly training to find a cure for her man.  What, by dogged perseverence, Kim Goodsell eventually worked out was that a defect in her copy of the gene LMNA was the likely cause of both of her conditions. It didn't make a cure more likely, but it made her feel that she wasn't taking this thing lying down. But in the process she really pissed off some of her consultants who couldn't see beyond the comfortable confines of their own specialty. 150 years ago Charcot said "In the last analysis, we see only what we are ready to see, what we have been taught to see. We eliminate and ignore everything that is not a part of our prejudices".

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