‘Harper’ the Myositis Patient!

One of the stranger diseases we come across is something that’s referred to as ‘Masticatory Myositis’ and it’s something we saw last month in a delightful little dog called Harper. Harper is a young Australian Shepherd owned by Ben and Georgie Brown. She initially came in having been very uncomfortable through the night. She was seen by Dr Steve Crouch and, by this stage, was in a degree of pain. She was swollen over the forehead and really struggled to open her mouth.  These signs are consistent with masticatory myositis – an inflammation of the muscles used in chewing food. It’s pretty unusual, however, for us to see this degree of pain and discomfort and normally presents as dogs having difficulty eating.

Steve admitted Harper and started her on intravenous fluids and pain relief. Initial bloodwork was unremarkable and so we started her on a combination of medications to reduce the muscle inflammation. Myositis is what we term an immune-mediated disease. This happens when the ‘recognition’ system within the immune system is altered so that certain cells within the body are perceived as being ‘foreign’.  Why that should happen with particular cell types and what suddenly sets that off is a mystery to us. In the case of masticatory myositis, not only does the immune system target muscle cells, it also selects the muscles of the head and cheeks in particular. The swelling associated with this usually make it quite difficult for affected dogs to open their mouths. Hence the common clinical presentation of dogs struggling to eat.

Over the course of the next 24 hours, it proved to be a real challenge for us to control the pain symptoms and poor Harper was a sorry sight. We realized that we were dealing with something more than a masticatory myositis and it become evident that the condition had become generalised throughout the body. This is particularly unusual and something we seldom see in general practice. The treatment involves a combination of supportive therapy, intravenous fluids, pain relief and specific anti-inflammatory medication to interfere with the immune system.

Over the next couple of days, we were able to bring the pain and inflammation under control and Harper eventually was sent home. Two days later, however, she had a relapse and was brought back in by Ben and Georgie. Further blood tests showed that she had a massive elevation of liver enzymes and was reacting to one of the drugs we were giving her. Several days of treatment followed but Harper gradually recovered to the point where she could cope at home. She gradually regained her strength over a further two weeks and is a much happier girl now.  Her liver enzymes are settling down and she is eating and drinking normally.

Unfortunately, one of the side-effects of the myositis is that the muscle function and form don’t necessarily recover and this has been the case with Harper. The muscle wasting has been quite dramatic and she looks like a shadow of her former healthy self. As a result of the generalized myositis, she’s lost the muscle over her forehead, cheeks, eyes, neck, back and legs. It’s questionable as to whether she’ll recover her former bulk. The good news is that she’s comfortable and is constantly improving with her mobility.

We’ll continue to monitor her enzymes and juggle the drug cocktail that she’s on. In masticatory myositis, we can often wean dogs off treatment altogether. In Harper’s case, it may be necessary to keep her on some form of anti-immune medication as an ongoing thing. In the meantime, Ben and Georgie are delighted to have her home again and improving day by day. Fortunately, they had insured Harper from an early age – I suspect they’re very grateful they did!

Well done to Dr Steve and the hospital team for getting on top of this complex case. We’re looking forward to seeing Harper for many years to come! 

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