Pathology of Skeletal Muscle Flashcards
What is associated with fascicles and contribute to muscle degeneration?
Satellite cells - small pool of tissue stem cells.
Type 1 muscle fiber type
Action Activity type Resistance to fatigue Power Color
Action: sustained force. Activity type: aerobic exercise. Resistance to fatigue: high. Power: low. Color: red.
Type 2 muscle fiber type
Action Activity type Resistance to fatigue Power Color
Action: fast movement. Activity type: anaerobic exercise. Resistance to fatigue: low. Power: high. Color: white/pale/tan.
What occurs in dermatomyositis?
Peri-fascicular atrophy.
Prolonged corticosteroid treatment and disuse causes atrophy of which fibers?
Type 2 fibers.
Regenerating muscle fibers are rich in…
Thus, they stain:
RNA
Basophilic
What age is common in Dermatomyositis?
What is the distinctive skin rash?
What are Grotton lesions?
What are the symptoms? (4)
What are the auto-antibodies involved? (3)
Adults: 4th-6th decade.
Iliac or heliotrope discoloration of eyelids associated with periorbital edema. Telangiectasias may also exist.
Scaly erythematous eruptions or dusky patches over knuckles, elbows and knees.
Proximal muscle involvement first.
1/3 develop dysphagia.
10% develop ILD.
Cardiac involvement is common.
Anti-Mi2 (rash and papules)
Anti-Jo1 (“mechanic’s hands”)
Anti-P155/P140 (paraneoplastic and juvenile)
Dermatomyositis increases the risk for what?
What is seen on histology and is classic?
Increased risk of visceral cancer.
“Peri-fascicular atrophy”.
Juvenile dermatomyositis onsets when?
What is classically involved?
What is seen on histology? (2)
Approx. 7 y/o.
GI tract.
Calcinosis and Lipodystrophy.
What is the presentation of Polymyositis?
How is it different than Dermatomyositis?
What are the distinct histological findings? (2)
Myalgia and weakness with symmetrical proximal involvement.
No cutaneous involvement.
Endomysial mononuclear infiltrate.
Random distribution of affected fibers (not perifascicular like in DMM).
What age is common for Inclusion Body Myositis?
What is the presentation?
What is the classic histological finding?
Late adulthood; > 50 y/o (most common inflammatory myopathy in patients > 65 y/o).
Slowly progressive muscle weakness that is most severe in Quads and distal UEs. Dysphagia due to esophageal and pharyngeal n. involvement.
Rimmed vacuoles.
What is first-line therapy for Dermatomyositis and Polymyositis?
What is given if they can’t take these drugs?
Which inflammatory myopathy does not respond to the first and second-line therapies?
Steroids.
Immunosuppressive drugs.
Inclusion body myositis responds poorly to steroids and immunosuppressives.
Chloroquine and Hydroxychloroquine cause what kind of myopathy?
Slowly progressive muscle weakness; type 1 fiber affected.
Thyrotoxic myopathy is characterized as…
Acute or chronic proximal muscle weakness.
What myopathy can be produced by alcohol?
Rhabdomyolysis -> myoglobinuria.
What are the X-linked muscular dystrophies? (2)
Duchenne muscular dystrophy (DMD) - more common, more severe.
Becker muscular dystrophy (BMD) - same genetic locus.
DMD is associated with which gene? Which protein?
How many are familial?
What is the progression of female carriers of DMD?
Xp21, loss of function of dystrophin.
2/3 are familial.
Increased CK, which increases the risk of CM.
How common is DMD?
When do symptoms onset?
1/3500 live male births.
Symptoms onset before 5 y/o; wheelchair by 10-12 y/o.
BMD onsets when?
What is the progression of the disease?
What is the amount of dystrophin in BMD?
Late childhood adolescence.
Nearly normal lifespan, but with cardiac disease.
Decreased, but not gone (like DMD).
What is Pseudohypertrophy of muscles?
Enlargement of muscles of lower leg associated with weakness; *increased bulk due to increased size initially, but leads to increased fat and CT.
What is Myotonia? How is it elicited?
What are the symptoms?
What is the inheritance of the disease? What protein is affected?
What is seen on histology?
Sustained involuntary contraction of a group of muscles. It can be elicited by percussion of the thenar eminence.
Skeletal muscle weakness (stiffness, problems releasing grip), cataracts, endocrinopathy and CM.
AD; CTG repeats of DMPK gene.
“Ring fiber” and “sarcoplasmic mass”.
What is the progression of Myotonic Dystrophy symptoms?
Gait first, then atrophy of facial muscles: ptosis and “hatchet face”, cataracts and CM.
Emery-Dreifuss Muscular Dystrophy (EMD) is associated with mutations in genes that encode what?
What is the triad of symptoms?
What are the 2 inheritance patterns?
Nuclear lamina proteins.
(1) Slowly humeroperoneal weakness, (2) CM w/ conduction defects, (3) early contractures of Achilles t., spine and elbow.
X-linked (EMD1) and AD (EMD2).
What is affected in Limb-Girdle Muscular Dystrophy?
What is the inheritance patterns?
The age of onset and severity of diseases…
Muscle weakness that preferentially involves proximal muscle groups.
Multiple AD and AR entities.
Vary greatly.
