Myopathies and Muscular Dystrophy

Question 1

list some clinical features of dermatomyositis

Answer 1

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.

Question 2

a patient comes in with a red coloured rash on the upper eyelids, what disease would it indicate

Answer 2

dermatomyositis

Question 3

what type of disease is dermatomyositis

Answer 3

it is a immunologic disease, the immune system is flawed

Question 4

what does is dermatomyositis primary target and how does it affect it

Answer 4

Capillaries seem to be the principal targets.

The microvasculature is attacked by antibodies and complement, resulting in foci of ischemic myocyte necrosis.

Question 5

In dermatomyositis the immune system attacks the body, what antibodies are detected

Answer 5

B lymphocytes as well as plasma cells are part of the inflammatory infiltrate that is seen in muscles.

Question 6

muscle biopsies from patients with dermatomyositis shows what type of infiltrate

Answer 6

mononuclear inflammatory cells

Question 7

when we look at the Immunohistochemical studies of a patient with
dermatomyositis what are the key indicators

Answer 7

CD4+ T-helper cells and the deposition of C5b-9 in capillary vessels.

Question 8

how does polymyositis differ from dermatomyositis

Answer 8

It differs from dermatomyositis by the lack of cutaneous involvement

Question 9

what does polymyositis target in the body

Answer 9

In this condition, the inflammatory cells are found in the endomysium.
CD8+ lymphocytes and other lymphoid cells surround and invade healthy muscle fibers.

Question 10

which features are common to polymyositis and dermatomyositis

Answer 10

• symmetrical proximal muscle weakness
• myalgia
• dysphagia

Question 11

which muscles are most severely affected by inclusion body mysotiis

Answer 11

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.

Question 12

which individuals are most likely to be affected by inclusion body myositis

Answer 12

Typically affects individuals over the age of 50 years. It is the most common inflammatory myopathy in patients older than age 65 years

Question 13

what are key features of inclusion body myositis

Answer 13

• 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

Question 14

what causes fiber necrosis and acute renal failure

Answer 14

acute alcohol myopathy

Question 15

which gene is affected by duchenne muscular dystrophy

Answer 15

p21 region of the X chromosome

Question 16

how does duchenne muscular dystrophy affect muscle fibres

Answer 16

Deficiency of dystrophin results in muscle fiber damage by uncontrolled entry of calcium into the cell

Question 17

what is the onset of duchenne muscular dystrophy

Answer 17

Onset is in early childhood (2-4 years), affected children show muscle weakness and pseudohypertrophy of the calf muscles (increased calf muscle size)

Question 18

what age do most affected individuals with duchenne muscular dystrophy die

Answer 18

Most affected individuals die before the age of 20 years of cardimyopathy

Question 19

what are some characteristics of beckers dystrophy

Answer 19

an X-linked recessive inherited disorder characterized by slowly progressing muscle weakness of the legs and pelvis.

Question 20

what does limb girdle muscular dystrophies mostly affect

Answer 20

It is characterised by progressive muscle wasting which affects predominantly hip and shoulder muscles

Question 21

what gene mutations cause mitochondrial myopathies

Answer 21

nuclear and mitochondrial genes

Question 22

what are the main characteristics of myotonic dystrophy

Answer 22

Characterized by gradual muscle weakness, wasting of facial, limb girdle and proximal limb muscles and myotonia

Question 23

what causes myotonic dystrophy

Answer 23

The disease is caused by expansions of CTG triplet repeats in the 3′-noncoding region of the myotonic dystrophy protein kinase (DMPK) gene,

Question 24

what is the key feature of myotonic dystrophy

Answer 24

Myotonia, a sustained involuntary contraction of muscles, is a key feature of the disease.

Question 25

what is the difference between myotonic dystrophy or other causes of myopathies compared to ion channel myopathies

Answer 25

They are a group of genetic defects in sodium, chloride, and calcium ion channels that are present in the myocyte membranes

Question 26

what are the most common clinical manifestations of ion channel myopathies( channelopathies)

Answer 26

include epilepsy, migraine, movement disorders with cerebellar dysfunction, peripheral nerve disease, and muscle disease.

Question 27

diseases of the lipid or glycogen metabolism produce 2 types of general muscle dysfunction

Answer 27

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.

Question 28

what are the names of 2 diseases associated with the lipid and glycogen metabolism

Answer 28

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.