CH 15--Disorders of Skeletal Muscles Flashcards
Diseases of skeletal muscles
—-Muscle Weakness—-
Causes: 1.--- NEUROGENIC i. \_\_\_\_\_\_\_ motor neuron paralysis: - spasticity - brisk deep tendon reflexes - NO significant muscle atrophy ii. \_\_\_\_\_\_\_\_\_\_motor neuron paralysis - loss of deep tendon reflexes - muscle ATROPHY!! Other causes: 2.--- Failure of neuromuscular transmission (e.g. myasthenia gravis) 3.--- Diseases of skeletal muscles (e.g. dystrophy)
Upper
Lower
Diseases of skeletal muscles
—-Muscular Dystrophy (MD)—-
Features: • \_\_\_\_\_\_\_\_\_\_ muscle diseases • \_\_\_\_\_\_\_\_\_\_\_onset • characteristic distribution • nonspecific histologic changes in the muscles (random atrophy & hypertrophy) • several different clinical types are recognized
inherited
childhood
Diseases of skeletal muscles–Muscular Dystrophy (MD)
4 Types:
- Duchenne
- Becker
- Limb-Girdle
- Facio-Scapulo-Humeral
FOUR TYPES OF MD!!
Diseases of skeletal muscles–Muscular Dystrophy (MD)-1
- DUCHENNE muscular dystrophy (DMD)
Pseudohypertrophic muscular dystrophy
A—-Features:
• MOST COMMON TYPE
• inherited, x-linked, recessive (boys)
• One of every 3500 live male births
• ABSENCE of structural protein called DYSTROPHIN!!
— it attaches the sarcomere (I & M bands) to cell membrane
• muscle appears LARGER in early stage due to FAT content (PSEUDOhypertrophic), especially the CALF muscles associated with weakness is an important clinical finding.
• ATROPHY and loss of myofibrils + hypertrophy of viable one.
B—-Manifestations:
• infant appears normal at birth
• disease is manifested in early childhood (age 5) by:
(a) SYMMETRIC weakness starting in PELVIC
girdle muscles
- difficulty GETTING UP from sitting position
(climbs on himself, walking his hands up his thighs)
- difficult walking (waddling gait; duck-like walk )
(b) rapidly PROGRESSES to involve ALL muscles
- weak, deformed legs
(confined to wheelchair by age 10-12)
- DEATH in 2nd decade due to failure of RESPIRATORY muscles.
Diseases of skeletal muscles–Muscular Dystrophy (MD)-2
- ________ muscular dystrophy (BMD)
Features
• very similar to DMD
• Affect boys but start at age 10 or later
• _________ IS PRESENT but ABNORMAL
• Clinical manifestations tend to be less severe
• Many people with BMD can LIVE LONG, active lives without using a wheelchair
Becker “BECKER THE BOY HAS DYS”
Dystrophin
Diseases of skeletal muscles–Muscular Dystrophy (MD)-3
- ______–_______ muscular dystrophy
Features • inherited, autosomal recessive • distribution: - pelvic and shoulder girdle muscles • no pseudohypertrophy • DEATH in 3rd or 4th decade
Limb-Girdle
Diseases of skeletal muscles–Muscular Dystrophy (MD)-4
- Facio-Scapulo-Humeral muscular dystrophy
Features • inherited, \_\_\_\_\_\_\_\_dominant (affect BOYS and GIRLS equally) • distribution: - face, neck and shoulder girdle muscles • normal life expectancy
autosomal
Treatment of Muscular dystrophy:
- There is NO specific treatment for any of the forms.
- Physical therapy to prevent painful muscle contractures
- Orthopedic appliances used for support
- Respiratory therapy
- Corrective orthopedic surgery may be needed to improve the quality of life in some cases
- Corticosteroids
KNOW
Diseases of skeletal muscles----Myasthenia Gravis----1 A.---Incidence: • common (1:4000 in USA) • age: 20-40 years • sex: more frequent in females (3:1) B.----Etiology: - autoimmune disease - many patients show \_\_\_\_\_\_\_\_ hyperplasia (75%) or thymoma (up to 40%) formation of AB (IgG) AGAINSTS acetylcholine (ACh) receptors on neuromuscular plate = blocks receptor function = prevents impulse transmission C.---Pathology: - NO microscopic abnormalities - IgG and complement on motor endplate
thymic
Diseases of skeletal muscles—-Myasthenia Gravis—-2
D.—Manifestations:
—muscle _________ which on repeated contractions
(worse during the later part of the day)
— can be restricted to _____ muscles (20% of cases),
leading to ptosis (drooping of eyelids)
and diplopia (double vision)
OR
— generalized, progressive weakness of facial
(difficulty chewing food & holding head upright)
and girdle muscles, eventual DEATH from failure of
____________muscles (80% of cases)
weakness
EYE
respiratory
Diseases of skeletal muscles—-Myasthenia Gravis—-3
E—–Treatment:
- drugs inhibiting acetyl cholinesterase, increasing acetyl choline (ACh) at ______ _________
-Thymectomy
F—-Prognosis:
-Can lead normal or nearly normal lives with treatment
motor endplate.
Diseases of skeletal muscles
——Botulism—–
Features:
• _________ of Clostridium botulinum blocks release of acetylcholine (ACh) at motor endplate
• causes GENERALIZED muscular WEAKNESS and DEATH from failure of respiratory muscles
exotoxin
NEOPLASMS of Skeletal Muscle
1—-Benign rhabdomyoma (rare)
2—-Malignant rhabdomyosarcoma
- MOST COMMON form of soft tissue SARCOMA in the _____________ population
- arise from striated muscles (orbit, retroperitoneum, extremities, etc.)
- children below _____ years
- HIGHLY malignant
- RAPID growth, early metastasis
pediatric
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