Myopathies and Muscular Dystrophy Flashcards
list some clinical features of dermatomyositis
a distinctive skin rash that may accompany or precede the onset of muscle disease.
Muscle weakness is slow in onset, is bilaterally symmetric, is often accompanied by myalgias, and typically affects the proximal muscles first.
a patient comes in with a red coloured rash on the upper eyelids, what disease would it indicate
dermatomyositis
what type of disease is dermatomyositis
it is a immunologic disease, the immune system is flawed
what does is dermatomyositis primary target and how does it affect it
Capillaries seem to be the principal targets.
The microvasculature is attacked by antibodies and complement, resulting in foci of ischemic myocyte necrosis.
In dermatomyositis the immune system attacks the body, what antibodies are detected
B lymphocytes as well as plasma cells are part of the inflammatory infiltrate that is seen in muscles.
muscle biopsies from patients with dermatomyositis shows what type of infiltrate
mononuclear inflammatory cells
when we look at the Immunohistochemical studies of a patient with
dermatomyositis what are the key indicators
CD4+ T-helper cells and the deposition of C5b-9 in capillary vessels.
how does polymyositis differ from dermatomyositis
It differs from dermatomyositis by the lack of cutaneous involvement
what does polymyositis target in the body
In this condition, the inflammatory cells are found in the endomysium.
CD8+ lymphocytes and other lymphoid cells surround and invade healthy muscle fibers.
which features are common to polymyositis and dermatomyositis
- symmetrical proximal muscle weakness
- myalgia
- dysphagia
which muscles are most severely affected by inclusion body mysotiis
Inclusion body myositis begins with the involvement of distal muscles, especially extensors of the knee (quadriceps) and flexors of the wrists and fingers. The weakness may be asymmetric.
which individuals are most likely to be affected by inclusion body myositis
Typically affects individuals over the age of 50 years. It is the most common inflammatory myopathy in patients older than age 65 years
what are key features of inclusion body myositis
- Patchy often endomysial mononuclear inflammatory cell infiltrates rich in CD8+ T-cells
- Focal invasion of normal appearing myofibers by inflammatory cells
- Abnormal cytoplasmic inclusions described as “rimmed vacuoles”
- Cytoplasmic inclusions containing proteins typically associated with neurodegenerative diseases, like beta-amyloid
what causes fiber necrosis and acute renal failure
acute alcohol myopathy
which gene is affected by duchenne muscular dystrophy
p21 region of the X chromosome
how does duchenne muscular dystrophy affect muscle fibres
Deficiency of dystrophin results in muscle fiber damage by uncontrolled entry of calcium into the cell
what is the onset of duchenne muscular dystrophy
Onset is in early childhood (2-4 years), affected children show muscle weakness and pseudohypertrophy of the calf muscles (increased calf muscle size)
what age do most affected individuals with duchenne muscular dystrophy die
Most affected individuals die before the age of 20 years of cardimyopathy
what are some characteristics of beckers dystrophy
an X-linked recessive inherited disorder characterized by slowly progressing muscle weakness of the legs and pelvis.
what does limb girdle muscular dystrophies mostly affect
It is characterised by progressive muscle wasting which affects predominantly hip and shoulder muscles
what gene mutations cause mitochondrial myopathies
nuclear and mitochondrial genes
what are the main characteristics of myotonic dystrophy
Characterized by gradual muscle weakness, wasting of facial, limb girdle and proximal limb muscles and myotonia
what causes myotonic dystrophy
The disease is caused by expansions of CTG triplet repeats in the 3′-noncoding region of the myotonic dystrophy protein kinase (DMPK) gene,
what is the key feature of myotonic dystrophy
Myotonia, a sustained involuntary contraction of muscles, is a key feature of the disease.
what is the difference between myotonic dystrophy or other causes of myopathies compared to ion channel myopathies
They are a group of genetic defects in sodium, chloride, and calcium ion channels that are present in the myocyte membranes
what are the most common clinical manifestations of ion channel myopathies( channelopathies)
include epilepsy, migraine, movement disorders with cerebellar dysfunction, peripheral nerve disease, and muscle disease.
diseases of the lipid or glycogen metabolism produce 2 types of general muscle dysfunction
In some, patients become symptomatic only with exercise or fasting, which may produce severe muscle cramping and pain, or even extensive muscle necrosis (rhabdomyolysis).
Other disorders of this type result in slowly progressive muscle damage, without episodic manifestations.
what are the names of 2 diseases associated with the lipid and glycogen metabolism
Carnitine palmitoyl transferase II deficiency is the most
common disorder of lipid metabolism to cause episodic
muscle damage with exercise or fasting. The defect in
this disorder impairs the transport of free fatty acids into mitochondria.
Myophosphorylase deficiency (McArdle disease) is one of the more common glycogen storage diseases affecting skeletal muscle; it also results in episodic muscle damage with exercise.
