How Polysaccharide Storage Myopathy Stopped us in our Tracks

Roley and Amy competing in March 2017 a horse affected by Polysaccharide Storage Myopathy

Readers Write In: How Polysaccharide Storage Myopathy Stopped us in our Tracks

When reader, Amy Greaves wrote in, we felt compelled to share her story to raise awareness of a condition that’s known very little about throughout the equestrian community. When faced with uncertainty and misdiagnosis, Amy’s love for her horse kept her searching for an answer.

Amy’s Story

I own a Welsh D X Tb called Prince Caspian (Roley). He turned seven a few weeks ago and I’ve had him since he just turned four. We like to do a bit of everything but, his forte is dressage. We were working at elementary level at home and competing at novice with great success; this year we managed to get three 1st places, two 2nds and one 3rd in the six tests we did before he went lame again. Unfortunately we have not yet managed to affiliate as every time we are about to, Roley, decides to go lame!

Last spring when Roley was still five, my farrier noticed he was wearing his near hind shoe down on one side more than his four other shoes. My trainer and I had noticed he was stumbling a couple of times per lesson too. When a physiotherapist came out to see us, she found Roley was quite tight on one side of his back, although he had not been before. I contacted the vets. Whilst I waited for my appointment, Roley slowly deteriorated. He started circumducting his hind legs in all paces, became heavier in the forehand and stiffer.

My vet came out and by which time, he was slightly lame in his near hind. She put him on a week of box rest followed by a week of small paddock turnout, respectively. Roley got worse quickly, at the end of his box rest he was extremely stiff, the lameness was much worse and he was clearly in pain. By the time the vet came back, he was still slightly lame but much better after being turned out. Because the lameness was made worse by box rest, she sent us to Rainbows Equine hospital for investigations as she predicted something such as arthritis or a spinal injury as we had both taken a fall out jumping the month before.


Despite investigation, Rainbows were unable to diagnose the problem. He underwent nuclear scintigraphy (bone scanning), which showed light up in most joints and X-Rays followed by ultrasounds. Results confirmed it wasn’t arthritis, his spine was fine, neck and legs etc. A splint was identified as inflamed, however this was something we were already aware of.

We went home and followed our rehab plan from Rainbows to bring him back to work, without aggravating his splint. I didn’t ride until the start of November. We had a few more trips to Rainbows, for his splint and when I told the vets repeatedly, he didn’t feel right; he was tripping more, was heavier in my hands, he was struggling to flex left. We had never had these problems before. We did repeat X-rays but they were all still clear. These problems were put down to laziness or bad attitude.

Roley relaxing in the field
Roley relaxing in the field

I gave up and believed maybe he was just lazy. We finished our rehab in January and went back to full work. We started competing again in March and it started to feel like I had my horse back; cheeky, lively, loving his work.

Trying to move on

We were getting ready for a competition in April; Roley at this point was very fit. The day we went out to competition, it was about 30 degrees and in the warm up I knew something wasn’t right. Roley was sluggish, he was ignoring my leg, he was leaning on my hands and burying his poll. Normally at shows he is more responsive so this was a concern. But with the first really hot day of the year and a supposed clean bill of health, I put it down to the heat and eating too much spring grass.

During our second test, Roley tripped during our first canter, stumbled and landed on the wrong leg during our counter canter section. We finished the test without any more faults but he was really struggling and lacking his usual spirit. I got off straight away, dowsed him in cold water as he was sweaty put couldn’t find anything else wrong. At home, he ate well, walked in hand fine, trotted up fine, flexed fine. Again, I put it down to the heat.


The next morning, I go to see him and he is very lame in all four. He was stood like he had laminitis but had no other symptoms of laminitis and no history of it. We put him on box rest with bute for a week, to treat him for laminitis and tendon issues etc in case he hurt himself when he tripped at the competition. He got drastically worse. My physiotherapist came a few days into the box rest and was horrified. Every muscle in his body was rigid by this point, he had tied-up (Azoturia) for the first time. She referred me to a vet she recommended but said there was nothing she could do. She also said that Roley looked have a Neurological problem and not ordinary lameness. We turned him out, to try and get him to move and loosen his muscles. At one point, he was so bad he lay down and we couldn’t get him to stand up again. He struggled to bend down to eat, we even caught him lying on his side to eat as it was easier than leaning down. Walking and bute slowly loosened him up enough to travel to the new vets ten days later.

Complete confusion

By this point, Roley was only lame in his hind legs. And no longer displayed neurological symptoms.  We had spinal X-rays which showed the precursors of kissing spines and hock x-rays that showed the start of arthritis in his hocks. He had his hocks injected and a spinal surgery to correct the vertebrae. He was sent home a few days later. Our rehab started well, he seemed to be improving for a few weeks.

Easter bank holiday Monday, we come down to see him in the morning and he could not move. It took four people and fifty minutes to walk him 400m to his stable. He was severely tied-up. He would sway side to side like a drunk, and was clearly in pain and distressed. We called the emergency vet. Due to the severity of the episode, she decided to check for abscesses, despite the chances of having an abscess in all four feet and effecting every muscle begin next to zero. She lifted his foot to check and Roley fell over. She realised how serious this was but didn’t know what to do. We were given a huge intravenous dose of bute and steroids.

Further investigation

This helped until the investigating vet came to us a few days later. The vets now believed that is was a neurological problem. Roley was now unfit to travel so we had a portable X-ray of his neck to check for damage or sign of Wobblers. We also had a lot of blood tests performed, including testing for Equine Herpes which can also have neurological symptoms. Our results were all clear.

Now my vet didn’t have a clue what to do. She contacted specialist vets across the UK. As a ‘last-ditch attempt’, the vet decided to take a muscle biopsy and send that to a specialist lab. A few weeks later, the results were in, Roley was diagnosed finally with type 2 PSSM, at which point we didn’t know what the future held.


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