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Recurrent Rhabdomyolysis in cyclists

Jun 5, 2018
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Dear fellow sufferers and cycling colleagues

I am a paediatrician from Brisbane. I would’ve been on the forum much earlier but I’ve had trouble logging in for quite a while realising it was my browser.

I am drinking my endura rehydration solution prior to cycling as we speak. I think I have cracked the case. I believe we may share a common condition related to an abnormal enzyme glycogen synthase, the same as in the horse polysaccharide storage disorder PSSM 1. It has never been described in humans.

I’ve had a number of investigations including muscle biopsy and metabolic testing. I have had the symptoms for 20 years and have had many episodes of rhabdomyolysis in both my thighs and unfortunately didn’t realise until reading this forum a few years ago that Others have the same symptoms and I’m not the only one suffering .

The pattern is similar. If I ride regularly I never get any symptoms at all, no cramps, no pain, I can ride as intense as I like and forever (I am a very average cyclist at best (see Mcgilla on Strava)) however if I have more than 2 days off my bike, I get rhabdomyolysis (extremely severe thigh pain varying in position) on trivial exertion eg walking. This goes against the grain of previously described rhabdomyolysis that is related to overexertion, inadequate fluids, hot weather etc. There is nothing in the literature about this condition in humans. I’m convinced it’s related to an abnormal glycogen synthase enzyme as a primary or secondary event. The enzyme is resistant to one of the protein kinases which doesn’t switch it off. Steph Valberg embarrassingly discovered this condition in horses 20 years ago. My theory for it not being that common is it tends to come on later in life and not many people are athletes like us (he he).
My first episode came on after doing a half marathon when I was 26 years of age. I stopped running for a few days and had my first bout of rhabdomyolysis in my calves. I started cycling 20 years ago and it’s only come to now to realise what the problem may be. I do believe we have a never described condition in humans, a variety of PSSM1 or very similar. It could also be possible that another protein called glycogenin could be at fault. The only way to prevent it is to exercise regularly without breaks (and have a low carbohydrate diet). The main reason I want to have this formally diagnosed is my wife just thinks I have obsessive cycling disorder and won’t let me take my bike on holidays even though I’m always limping around in severe pain even after a short walk ( as well as help you).


Glycogen synthase is upregulated producing too many 1,4 glycosidic bonds compared with 1,6 bonds which adds extra glucose onto the glycogen chain. It continues to be upregulated If there are too many rest days (>2 days) and is not turned off sufficiently once exercise is has begun. I suspect it is the polysaccharide storage disease described in horses, never in humans. It disappointingly has never been described in humans but it looks as though most people who are posting this have the same condition, guessing it is more common than we think. There are 15 glycogen storage diseases and this has never been described in humans and I suspect we are onto something.

It has nothing to do with stretching or any other condition. Unfortunately I don’t think any treatment will be available for cure. The key is to exercise frequently, the draft horses have at least a 20 minute run per day and they don’t get the disease, They also swear by a low carbohydrate diet which may be a possibility. It does appear in the muscle biopsy of horses that there is an abnormal glycogen. My muscle biopsy did not show abnormal glycogen so I suspect it is due excess normal glycogen And unable to turn off the glycogen synthase which keeps over producing


Add on note: Please spread the news : send your saliva to Invitae in San Francisco, it is a metabolic lab analysing the glycogen storage panel DNA (and rhabdomyolysis panel) cost $250. I’m sending mine from Australia. It may not be the answer but it’s worthwhile checking so as many cyclists as possible who have the condition after days off the bike please send saliva to Invitae in San Francisco. You can mention my name.

regards

Mike McGill

Brisbane
 
Jun 5, 2018
16
2
535
Breaking news: I have the results. It isn’t a Glycogen synthase abnormality but I was close. It is phosphorylase kinase deficiency a rare X-linked mutation of PHKA1 gene causing reduced levels of muscle phoshorylase kinase and inability to breakdown muscle Glycogen (GSD9d). My girls are carriers. No treatment. Just exercise regularly or not at all, I just have to be careful.
I encourage you to contact Dr Dave Coman, Metabolic Physician in Brisbane Australia : reception@drdavidcoman.com.au who can arrange a Glycogen storage DNA analysis (free if you live in the states) of your saliva to Invitae in San Francisco.
regards
Mike
 

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