Pathology- Myopathies Flashcards
What is a denervation atrophy?
any process that affects the anterior horn cells or axon in the PNS
What is the most common form of denervation atrophy?
Wednig-Hoffman disease
What is the onset and mortality rate of Werdnig-Hoffman disease?
onset from birth-4 mo, death within 3 years, it has type 1 spinal muscular atrophy
What is the inheritance of Werdnig-Hoffman disease?
autosomal recessive
What are the clinical features of Werdnig-Hoffman disease?
absence of stretch reflexes, flaccid paralysis, floppy babies, lack sucking ability, respiratory failure
What are the 2 most common X-linked dystrophies?
Duchenne and Becker
Is DMD or BMD more severe?
DMD
What is mutated in DMD?
dystrophin gene on Xp21
What are the clinical features of DMD?
muscle fiber size variations, increase in internalized nuclei, degeneration necrosis and phagocytosis of msucle, increase in connective tissue, regeneration os muscle fibers.
What stain can you use for a muscle to see dystrophin and thus be able to Dx DMD?
immunoperoxidase stain, which should stain dystrophin at the periphery of the normal muscle fibers
Where in the body does DMD affect?
begins in the pelvic girdle and extends to the shoulder girdle.
What type of tissue increases in the calf of DMD pt’s?
adipose tissue
What is the clinical presentation of DMD?
cardiac failure, mental retardation, CK increases during 1st decade and decreases muscle mass decreaases, death from respiratory or cardiac failure or infection
What is myotonic dystrophy?
impared muscle relaxation
What is the msot common form of adult dystrophy?
myotonic dystrophy
What is the inheritance of myotonic dystrophy?
autosomal dominant
What is the clinical presentation of myotonic dystrophy?
atrophy of type I fibers and hypertrophy of type II fibers, stiffness, cataracts, CNS problems, facial and jaw muscles affected
What muscle can you percuss on the pt to Dx myotonic dystrophy?
thenar muscles, where the thumb moves sharply into opposition and adduction and slowly returns to an initial position
What is the clinical presentation of thyrotoxic myopathies?
proximal muscle weakness, exophthalamos
What causes thyrotoxic myopathies?
decreased thyroid fxn –> muscle crtamps, movement and reflexes slowed
Who is affected more by thyrotoxic myopathies, males or females?
Males 4:1
What is ethanol myopathy?
binge drinking –> acute myopathy –> rhabomyolysis –> myoglobinuria –> possible renal failure
What is drug-induced myopathy?
steroids can cause proximal muscle weakness and muscle atrophy
What happens in myasthenia gravis?
loss of Ach receptors from an increas ein Ach Ab’s
What are the causes of myasthenia gravis?
thymic hyperplasia (65%) or thymomas (15%)
What are the Sx of myasthenia gravis?
extraocular muscle ptosis and diplopia, generalized weakness, respiratory ocompromise (major cause of death), decrease nerve conduction with repetitive stimualtion
What is affected in Lambert-Eaton syndrome?
the NMJ
What does Lambert-Eaton syndrome develop as?
a paraneoplasic process that causes small cell CA in 60% of pts
What are the clinical features of Lambert-Eaton syndrome?
proximal muscle weakness, increase in nerve conduction with repetitive stimulation
Is there a benefit with AchE blocking in Lambert-Eaton syndrome?
No
What causes Lambert-Eaton syndrome?
autoimmunity to Ca++
