INCLUSION BODY MYOSITIS and INCLUSION BODY MYOPATHY.

INCLUSION BODY MYOSITIS and INCLUSION BODY MYOPATHY.

Bill Tillier Calgary, Alberta February, 2012.

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IBM classification.

? Inclusion Body Myositis and Inclusion Body Myopathy are classified as types of muscular dystrophy.

? Muscular dystrophy: ? Idiopathic inflammatory myositis (IIM) disorders:

? Dermatomyositis (DM) ? Polymyositis (PM) ? Inclusion body myositis and inclusion body myopathies.

? Idiopathic means the cause is unknown.

? There are similarities between PM & IBM (and also big differences) but DM seems to be quite different.

? People often confuse MD with a different disorder; MS: multiple sclerosis, a disorder affecting the nerves.

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General information 1.

? Called myositis to emphasize its characteristic muscle inflammation.

? Sporadic inclusion body myositis (sIBM) is the most common form of IBM disease.

? Sporadic means it just shows up in people (it's not inherited, it is considered an acquired illness).

? sIBM is a relatively rare disorder, its incidence is about 15 per 1,000,000 in the overall population, but rising to over 50 per 1,000,000 in people over 50 (doi: 10.1136/jnnp.

2007.138891).

? Statistically, slightly more males are affected than females.

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General information 2.

? sIBM is age-related, as we get older, it gets more and more common. Age of onset (when you first notice it) is about 60 but this varies widely (20% of cases appear in the forties).

? Symptoms emerge slowly, over months or years.

? The causes of sIBM are currently unknown.

? They have tried various treatments for sIBM, but none has so far been shown to slow the progression.

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General information 3.

? sIBM is a progressive disorder of skeletal muscle cells: as more and more cells are affected and die off, the muscles shrink and become progressively weaker.

? The rate of progression in patients varies widely. Progression tends to be faster in men & in patients with later onset.

? The progression rate varies in different muscle groups: lower leg muscles show the greatest decline, followed by forearm muscles and then upper leg muscles.

? "characteristic distribution of affected muscles: finger flexors, quadriceps, lower leg muscles with relative sparing of shoulder and hip abductors and neck muscles" doi:10.1093/brain/awr258

? The following diagram outlines the weakness seen.

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