How rare is Myositis?

diagnosis of polymyositis

Myositis is a rare disease diagnosed in just 1 in 100,000 people a year.*  Some people think the number should be higher as many cases may go unidentified. It is often mistaken for the symptoms of aging even by sufferers or fibromyalgia or depression.  Many patient see seven or more doctors before getting the correct diagnosis of Myositis. This is what happened to me.
The three main types of myositis, or inflammatory myopathy, are polymyositis, dermatomyositis, and inclusion body myositis. All 3 diseases involve chronic muscle inflammation, accompanied by muscle weakness.  

  • There are 2 separate ages of onset: 10 - 15 years and 45 - 60 years.
  • Female to male ratio is 2 :1 except in inclusion-body myositis (IBM) where it is reversed.
  • Prevalence of the disease is the highest in the Japanese.

* 2013
American College of Rheumatology


  1. Hi, I write a blog too, I started off being diagnosed with Difusse systemic scleroderma, Raynauds and Sjogrens, but I knew they did not explain my loss of strength and incredible lack of stamina and weakness,then they realised I had a myopathy, possibly polymyositis , but I am leaning towards IBM as it has been coming on for a few years, suddenly couldn't ride a bike and steadily getting worse. I'm on prednisone and ethotrexate and bunch of other pills for various bits that are failing!

  2. Hi Chris, great to hear from you (don't you just love it when someone adds a comment!) I have Sjogren's too - it seems you get an autoimmune condition you get more than one. Fun huh? i'll check out your blog and add it here.


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