Myopathies Flashcards
MUSCULAR DYSTROPHIES
What are muscular dystrophies characterized by?
Progressive muscle weakness and wasting
What serum level is oftentimes elevated in muscular dystrophies?
creatine kinase
A genetic defect on the short arm of the X chromosome has been identified in _____ dystrophy
Duchenne
This genetic defect found in Duchenne’s cdes for what protein? What is the affect?
dystrophin
Levels are markedly reduced or absent in the muscle of these patients
Are dystrophin levels affected in the Becker variety of muscular dystrophies?
No
What medication improves muscle strength and function in boys with Duchenne dystrophy?
Prednisone
What things must be avoided and what things are encouraged in these patients?
Bed rest is associated with a worsening of the disease
PT and orthopedic procedures may help counteract deformities or contractures
MYOTONIC DYSTROPHY
Myotonic dystrophy is a slow, progressive, inherited disorder that manifests in the __ or __ decade of life
3rd or 4th
How many types of myotonic dystrophies have been determined?
2
What are 3 muscular symptoms of myotonia?
- muscle stiffness
- marked delay in muscle relaxation following contraction
- weakness and wasting of the facial, SCM, and distal limb muscles
What are 6 clinical features of myotonia?
- cataracts
- frontal baldness
- testicular atrophy
- diabetes mellitus
- cardiac abnormalities
- intellectual changes
What drug may be helpful when myotonia is disabling?
Sodium channel blockers such as…
- phenytoin
- procainamide
- mexiletine
True or False
Associated weakness and the course of myopathy are influenced by treatment
False
MYOTONIA CONGENITA
Myotonia congenita is commonly inherited as a _____ trait
dominant
The responsible gene on chromosome 7 is responsible for what?
encoding a voltage-gated chloride channel
When do symptoms of myotonia congenita develop?
early childhood
What are the 2 signs and symptoms of myotonia?
- muscle stiffness that is enhanced by cold and inactivity
- muscle hypertrophy
What relieves muscle stiffness?
exercise
What durgs are used to treat myotonia congenita?
- procainaminde
- tocainide
- mexiletine
- phenytoin
INCLUSION BODY MYOSITIS
Inclusion body myositis begins _____, usually after middle age
insidiously
What is the main characteristic of inclusion body myositis?
progressive proximal weakness of first the LEs and then the UEs
Where does muscle weakness often begin in inclusion body myositis? (LE and UE)
- the quadriceps femoris
- forearm flexors
What confirms the diagnosis of inclusion body myositis?
muscle biopsy
What drug therapy has been found to have a mild benefit on inclusion body myositis?
Intravenous immunoglobin (IVIG) therapy
MITOCHONDRIAL MYOPATHIES
What can be seen on pathologic examination of skeletal muscle with the modified Gomori stain in patients with mitochondrial myopathies?
characteristic “ragged red fibers” containing accumulations of abnormal mitochondria
What 2 signs do patients with mitochondrial myopathies present with?
- progressive external ophthalmoplegia
- limb weakness that is exacerbated or induced by activity
Some patients with mitochondrial myopathies present with what type of dysfunction?
CNS (epilepsy, ragged red fiber syndrome, or MERRF)
What does the acronym MELAS stand for?
Myopathy
Encephalopathy
Lactic Acidosis
Stroke-like episodes
What type of patients do mitochondrial myopathies develop?
- AIDS patients receiving zidovudine
- HIV1 patients receiving HAART
ASSOCIATED MYOPATHIES
What are some associated disorders myopathy may occur with?
- chronic hypokalemia
- endocrinopathy
Myopathy may develop in patients taking what drugs?
- corticosteroids
- chloroquine
- colchinice
- clofibrate
- emetine
- aminocaproic acid
- statin drugs
- bretylium tosylate
Weakness due to myopathy is mainly _____.
proximal
Preexisitng myotonia may be exacterbsated or unmasked by what drugs?
- depolarizing muscle relaxants
- beta-blockers
- fenoterol
- ritodrine
- diuretics
