It has been quite a while since I have written a blog, in part due to the whirlwind of changes in my life right now. One of the big things that has happened this year is I learned about PSSM. It is something I had heard about for years, but didn’t know much about and never would have thought one of my horses had. Thanks to a client and friend whose horse was diagnosed this spring with PSSM type 2 I started to learn that PSSM is not just a Quarter Horse disease. It is a Thoroughbred disease, a Warmblood disease, an any breed of horse disease. I make no claims to be an expert here, but I wanted to share with you my journey into PSSM in the last 6 months and how widespread and frequently misdiagnosed PSSM really is.
So first off, lets cover some basics. PSSM stands for Polysaccharide Storage Myopathy. It is a term used to describe several different diseases that cause a horse’s muscles to tie up or other unusual presentations of the musculature of the horse. There are 2 types of PSSM – Type 1 and Type 2. Both are genetic diseases and testable through a genetic test performed on a hair sample.
Type 1 is a mutation of a gene that results in abnormal glycogen storage in the horse’s muscles. This causes severe muscle pain and muscle cramps. You can read more about Type 1 PSSM here.
Type 2 PSSM is a collection of diseases that result in tears, gaps, or other issues with the actual muscle tissue of the horse, not just the storage of glycogen in the muscle. Type 2 PSSM causes muscle wasting, muscle cramps, and systemic pain. You can learn more about PSSM 2 here. PSSM 2 is further broken down into 6 testable genetic mutations. P2, P3, and P4 are forms of Myofibrillar Myopathy or MFM. MFM primarily affects skeletal muscles, although it can also affect the heart. These mutations cause muscle weakness and muscle wasting. Px is a form of Recurrent Exertional Rhabdomyolysis (RER), which results in issues with calcium regulation in the muscles. This causes muscles to not always fire properly when the horse wants them to. The other two testable genes, P8 and K1, are not yet researched enough to understand how they cause PSSM symptoms.
So now that we have a basic understanding of what PSSM is, let me explain to you how I came to learn more about PSSM and the crazy journey it has been ever since.
In April of this year my client and friend decided to do a blood draw on her horse, Happy, to check for any issues. She didn’t suspect anything, but wanted a base line as he got older. We were lucky that blood was drawn the Wednesday after we got lost on our Sunday trail ride. When she got results back he had elevated AST, BUN/Creatine ratio, LDH, CPK, and Potassium. Our vet immediately suspected PSSM even though her horse is a Standardbred. She did the genetic testing and he was diagnosed with MFM.
We were so lucky with the timing of the blood draw because blood work does not always show muscular issues unless there has been a recent episode of tying up. We didn’t understand it at the time, but after our excessively long trail ride my client’s horse wouldn’t get off the trailer. We now believe he tied up in the trailer and that was what created the elevated blood levels.
This horse also had issues with cantering that we had attributed to him being a gaited Standardbred, difficulty using himself properly, severe lethargy, and aggression on a lunge line. Most of this I chalked up to breed, conformation, arthritis, and poor previous training. As my client started to treat her horse his issues started getting better and better. He now has a proper 3 beat canter, is forward off the aids with minimal whip, and a much more relaxed, less anxious horse.
All of this got me thinking.
My mom’s horse, Snuffy, has always had difficulty cantering. He got past the refusal and settled on pinning his ears when asked to canter because he is a good boy who always tries to please. He had a weird lameness in his right hind that would come and go. We had thought it was arthritis of his hock, but saw little improvement with injections. He was rapidly declining and at 15 years old I was beginning to think he might be retired sooner rather then later despite monthly injections for the presumed arthritis, supplemental joint support, a decreased work load, and everything else I could try to keep him comfortable.
As I watched my client’s horse soften through his body and move better I started to notice the thick, tight muscles on Snuffy. I am also trained in Equine Massage and had noticed when I massaged Snuffy that his muscles were unusually tight and knotted, but always attributed it to the pain he was in from his arthritis. All these signs I swept under the rug as “normal”.
On a whim I decided to try him on the supplements that seemed to be helping my client’s horse. I noticed an immediate, drastic change. Suddenly the horse that would barely move had a motor. He started to have more better days and fewer bad days. I began to think there was hope of him continuing on with his career as a lesson and pleasure horse. After I saw the results I sent a test in for Snuffy and he came back n/Px. He is heterozygous for RER.
Flash forward to now, September, and 3 months into treatment Snuffy is a brand new horse. He now willingly canters without so much as an ear flick. He has lift through his gaits I haven’t seen in the 5 years I have known him. He is able to actually lift his back and begin to use himself. His tight quadriceps are slowly loosening and stretching. A horse I never suspected of having a muscle disorder turned out to have been severely affected. I was mindblown.
I started to see PSSM everywhere. All these horses that were tight through their bodies, explosive in work, unwillingly to cooperate — what if they all had PSSM? At the same time I questioned how I could have gone my whole life only ever hearing of it in passing if PSSM affected so many horses. Even while I questioned my new viewpoint, I was starting to ride, train, teach, and see everything differently. Suddenly what I had seen as training issues became physical issues. And the results have spoken for themselves.
A few weeks after diagnosing and beginning treatment on Snuffy I decided to test my whole herd. I was seeing the symptoms everywhere and was going crazy from it. Testing was supposed to prove to me I was wrong and PSSM isn’t everywhere. It was supposed to reassure me that horses do dissent and are difficult to train simple because that is who they are or what they have been taught to be. I needed that world view because otherwise I knew that every time I had pushed a horse through something I had probably done wrong by that horse.
I sent in samples from Elijah, one of my lesson horses, as well as my two personal horses, London and Lucy. I didn’t want to believe any of them had it although I wondered about Lucy. I had thought about it with her before retiring her 2 years prior, but dismissed the thought since her blood work always came back normal. Her tight muscles, grumpy attitude, and instability were diagnosed as a neurological issue likely stemming from a previous neck fracture and chronic ulcers.
When I got results back I was stunned in the most gut wrenching way.
Lucy came back with 2 mutations (P2 and Px, both heterozygous). I wasn’t terribly surprised yet was both disappointed because I had planned to breed her and excited about the prospect of making her more comfortable and maybe sound again. As I have managed her I had my first ride on her a month into treatment. She felt better than she ever had in the 5 years I have owned her. She is now able to walk, trot, and canter comfortably. Her canter is better and more natural looking than I have ever seen it before and all those days of bucking in the canter all make sense. She no longer refuses hills or looks like she may fall. I am hoping that she will be able to resume a full riding career and perhaps jump in the future as she builds muscle. She still has her aggression issues, her body sensitivity, and her anxiety, but she is so much happier, more relaxed, and seems to be in a lot less pain. Lucy definitely has both mental and physical issues on top of the PSSM so it will be a journey to see how much I can continue to improve her.
Elijah came back with 3 mutations (P2, P8, and Px, heterozygous for all). I had begun to convince myself he had it because he seemed to do better when he stole Snuffy’s grain with all the special supplements. I had always assumed his pogo stick warmup trot was a result of the anxiety we never seemed to shake and his desire to run on his forehand was from his forward nature and dislike for “work”. I had always said he had a poor work ethic but endless energy for the fun stuff. Turns out I was all wrong, yet I never would have gone searching for answers. Eljah was fun, had tons of personality and quirks, and seemed pretty happy with his life even with the arguments we had about using himself better. Now I just have to look on him in wonder. What an incredible horse to be able to live in so much chronic pain and hide it so well.
Elijah is getting closer to managed, although he still has better and worse days. With him I notice it the most in his ability to engage his hind end and canter instead of running on his forehand. It used to be a test of wills to almost force him onto his haunches and now he is quite comfortable collecting the trot. The canter still has issues and I don’t know if it is all PSSM that could be managed better or if there is another factor. Elijah’s recent history of misbehaving in the winter and charging at fences suddenly made sense to me as he began to return to the younger version of him that I had known. I had thought he had matured when I got him back a year ago, but I think he had just become used to the constant pain that unmanaged PSSM causes. Even when I first knew Elijah at 5 years old I am sure he was starting to be symptomatic. I’m sure that is why he seemed burned out when I purchased him and why he was retired from the track. I have confidence that if I get his PSSM completely managed he will have the most incredible work ethic, effortless collection, and superstar potential.
London was the one I didn’t want to see. This was my 5 year old with front feet issues that had suddenly gone downhill in the spring despite trying Epona shoes, extra padding, and rest. He is P4/P4, a particularly devastating form of MFM that also inhibits the T-Cells in the horse’s immune system. Suddenly everything was adding up. The intermittent lameness. The days he would be crippled and massaging his cramped shoulder would make him sound. The strange front foot lameness that didn’t look severe on x-ray and didn’t seem different on soft versus hard ground. The fact that his unbalanced, downhill canter had in fact seemed to get worse as he progressed in his training, not better. The extreme back soreness he experienced after our drive from California to Kentucky for the RRP. The fact that every cut, scrape, and bump seemed to get infected and put him on antibiotics. All caused by PSSM and I never would have guessed even while I was asking my vet, farrier, and friends for suggestions and trying to get to the bottom of his issues.
This is really why I am writing this blog post. My 5 year old is now sitting in pasture some days almost unable to walk despite my best efforts to treat this disease. A horse I thought had all the potential in the world now may not ever be sound again. I haven’t given up hope yet, but I also know that the progression of this disease can be fast and ruthless and I don’t want to be the one that waits too long to end the suffering. All of this I never would have understood if not for my friend’s horse getting diagnosed. I probably would have been one of many others who ended up putting a young horse down for crippling lameness and a mystery disease without ever being able to put a name to it or having a flying chance of treating it. And my other horses, my cleint’s horses, my horses in training…I would have just kept pushing them and trying to train them through their physical limitations. My mare would still be retired in pasture in severe pain and suffering while I thought it was a neurological disorder. I would have let her pass that on to a foal to suffer the exact same fate. Elijah would have kept pretending he was fine while I got increasingly pushy about him using the back muscles that were tight and cramped. Snuffy would have kept trucking along until I eventually retired him, hoping he could at least be comfortable out to pasture.
I am so glad that I got to learn about this disease and help the horses I have that suffer from it. Yet I am also so unbelievably saddened that I didn’t know sooner and that I have pushed these horses through pain so many times thinking it was tension or laziness. And I am devastated to know that PSSM isn’t just some disease that a few horses out there have. I tested 4 TBs and every single one of them came up positive. Not just 4 TBs with undiagnosed issues, but the 4 TBs I happened to own. Statistically that says that PSSM is everywhere. Now with my PSSM goggles I can see it. I can see the pain and suffering so many horses go through without anyone thinking it is abnormal. I know that “normal” is so often riddled with pain and discomfort that we can’t even see it anymore. So please, look around you. Look at all the “normal” horses in your life and look deeper. Look for that tight musculature, look for the pain, and test them even if you don’t think they have it. Now that I know, I can’t unsee.