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1A. The most common types of myopathies and myositis: Difference between revisions

1A. The most common types of myopathies and myositis (view source)

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(Created page with "= Myopathies = A myopathy is a disease of the muscle itself, not involving innervation or the NMJ. There are many different types. === Etiology === * Hereditary myopathies ** Progressive muscular dystrophies *** Duchenne muscular dystrophy *** Becker muscular dystrophy *** Myotonic dystrophy *** Facioscapulohumeral muscular dystrophy (FSHD) ** Congenital myopathies ** Metabolic myopathies *** Mitochondrial *** Pompe disease – rare but treatable, so important to recog...")
 
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A myopathy is a disease of the muscle itself, not involving innervation or the NMJ. There are many different types.
A myopathy is a disease of the muscle itself, not involving innervation or the NMJ. There are many different types.


=== Etiology ===
== Etiology ==
 
* Hereditary myopathies
* Hereditary myopathies
** Progressive muscular dystrophies
** Progressive muscular dystrophies
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Duchenne muscular dystrophy is an X-linked recessive deletion of the dystrophin gene.
Duchenne muscular dystrophy is an X-linked recessive deletion of the dystrophin gene.


=== Clinical features ===
== Clinical features ==
The typical feature of myopathy is symmetrical proximal muscle weakness. Muscle pain is not typical.
The typical feature of myopathy is symmetrical proximal muscle weakness. Muscle pain is not typical.


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Congenital myopathies have good prognosis and slow development.
Congenital myopathies have good prognosis and slow development.


=== Diagnosis and evaluation ===
== Diagnosis and evaluation ==
Diagnosis is based on phenotype, EMG findings, muscle biopsy findings, and genetic studies. On EMG, short motor unit potentials (MUPs) can be seen.
Diagnosis is based on phenotype, EMG findings, muscle biopsy findings, and genetic studies. On EMG, short motor unit potentials (MUPs) can be seen.


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In any person with myopathy, it’s important to rule out hypothyroidism.
In any person with myopathy, it’s important to rule out hypothyroidism.


=== Treatment ===
== Treatment ==
Unfortunately, there is not much to offer patients with myopathies except treating any underlying cause, if present. Physiotherapy is always important. Steroids delay the need for wheelchair in Duchenne by 2 years.
Unfortunately, there is not much to offer patients with myopathies except treating any underlying cause, if present. Physiotherapy is always important. Steroids delay the need for wheelchair in Duchenne by 2 years.


== Myositis ==
= Myositis =
Myositis is a subtype of myopathy where there is inflammation of muscle.
{{#lst:Inflammatory myopathy|neurology}}
 
=== Etiology ===
 
* Polymyositis (PM)
* Dermatomyositis (DM)
* Necrotising myositis
* Inclusion body myositis (IBM)
* Overlap myositis
* Paraneoplastic myositis
 
Dermatomyositis and necrotising myositis can be primary or secondary to adenocarcinoma.
 
=== Clinical features ===
In most types of myositis there is proximal weakness, atrophy, and muscle pain. The only exception is inclusion body myositis, in which there is distal muscle weakness. IBM affects elderly.
 
In dermatomyositis there are also skin symptoms, namely heliotrope rash and Gottron papules. Polymyositis is like dermatomyositis but without skin symptoms. Necrotising myositis is similar to them but worse.
 
=== Diagnosis and evaluation ===
The creatine kinase (CK) is elevated in most cases. MRI can show the distribution and extent of inflammation and can guide the location for biopsy.
 
Muscle biopsy is usually required for diagnosis. On muscle biopsy, inflammation, and MHC-I expression (which is usually not expressed on muscle) can be seen. In necrotising myositis, necrosis can be seen, and in IBM, vacuoles are present.
 
EMG can differentiate between neurogenic and myopathic problems.
 
In dermatomyositis and necrotising myositis it’s important to rule out adenocarcinoma.
 
=== Treatment ===
The treatment is usually immunosuppressants, usually steroids + azathioprine or methotrexate. Immunosuppressants is not effective for IBM, however.
[[Category:Neurology 2]]
[[Category:Neurology 2]]