Polymyositis Overview : Johns Hopkins Myositis Center

Polymyositis Overview : Johns Hopkins Myositis Center

January 14, 2020 1 By Jose Scott


(dramatic music) – So polymyositis literally
means many muscles inflamed. Poly meaning many, myo
muscle and itis inflammation. That term has really developed over time as our understanding grew. In years past it was appreciated to be
inflammation in the muscles and over time I think we’ve
realized that that turned out to be a pretty broad diagnosis
and now we understand more about it. (dramatic music) Polymyositis, in some rare
cases, actually affects children, but the majority are adults. Over the age of 18 we often see two peaks. But really it can affect anyone
throughout the age spectrum. We sometimes see a peak
around younger people in their 30’s or 40’s and then
again in the 60’s and 70’s. Like most autoimmune
diseases it preferentially does affect woman. Woman are about three times as likely as their male counterparts
to have polymyositis. (dramatic music) I think one of the most important things that we now appreciate is
that polymyositis really is a diagnosis of exclusion. And what I mean by that is that we should rule out
five main things as physicians before giving the patient that diagnosis. The things that we now think about are a cousin to polymyositis, which is immune-mediated
necrotizing myopathy. That’s a giant mouthful. But essentially, the
difference really lies under the microscope. The patient may feel the same way. Weakness in the shoulders,
weakness in the hip muscles. However, under the microscope
the main features differ. And it’s important because
the treatment may differ. The second thing we think about now is whether this is part
of an overlap syndrome. In the rheumatologic diseases
many diseases travel in pairs. The most common overlaps with polymyositis would be polymyositis in
combination with scleroderma, which is a cousin to polymyositis, which may affect internal
organs as well as the skin. Rheumatoid arthritis, in rare cases lupus, and another rare disease
called Sjögren’s syndrome, which often has dry eyes or dry mouth. Polymyositis is frequently
not seen on it’s own, but rather in concert with
other autoimmune diseases. The third thing to think
about when we think about a diagnosis of polymyositis is something called the
atisynthetase syndrome. That’s discussed elsewhere
in this video series, but essentially again,
that is muscle weakness in concert with a lot of other features in addition to just the muscle. It may affect the lung,
it may affect the joints and it may cause Raynaud’s phenomenon, which is turning bluish color of the hands in cold or stressful situations. And again, it’s not seen just by itself and it’s important to label that as such. And the other two things to think about are actually mimics to polymyositis. Polymyositis can look just like some adult onset muscular dystrophies. It can have the exact same symptoms and even under the microscope
we may see inflammation. It takes an astute physician
and a careful workup to make sure that polymyositis
is in fact not another mimic. (dramatic music)