Muscle disease pathology Flashcards
What are the properties of type I myofibers?
Red due to high myoglobin and mitochondrial content, high in oxidative activity, low in glycolytic capacity, slow contraction, capable of continuous and repeated contraction
What are the properties of type II myofibers?
White due to low myoglobin and mitochondrial content, low in oxidative activity, high in glycolytic capacity, fast contraction, cannot maintain repeat contraction
What are the characteristics of myopathic myopathies?
Associated with scattered myofiber necrosis and regeneration
What are the characteristics of inflammatory myopathies?
Myopathic and characterized by inflammatory infiltrates and/or intracellular inclusions
What are the characteristics of neuropathic changes in skeletal muscle injury?
Fiber type grouping and grouped atrophy, target fibers
What are the causes of type II myofiber atrophy?
Disuse, often due to prolonged bed rest, hospitalization, casting; endogenous (Cushing syndrome) or exogenous glucocorticoid exposure; hyperthyroidism
What are the two primary categories of inherited disorders of skeletal muscle?
Muscular dystrophies and congenital myopathies
Which inherited disorders of skeletal muscle are progressive and which are static?
Muscular dystrophies are progressive, congenital myopathies are usually static
What protein complex is associated with many muscular dystrophies?
Dystrophin-glycoprotein complex
What is the general mechanism of dystrophin-glycoprotein-associated muscular dystrophies?
The defective dystrophin-glycoprotein complex causes defects in mechanical stabilization and signaling interactions between the cytoskeleton, cell membrane, and extracellular matrix; coupling of the sarcolemma to the extracellular matrix proteins and the intracellular skeleton
What are the two types of dystrophinopathies?
Duchenne and Becker muscular dystrophy
What is the primary difference between DMD and BMD?
Duchenne presents much earlier in life; DMD is usually associated with a frameshift mutation or deletion of the dystrophin gene, while BMD is usually associated with a point mutation in the dystrophin gene, which leads to a defective but somewhat functional protein
What is the inheritance pattern of DMD and BMD?
X linked recessive
What is the prognosis of patients with DMD or BMD?
DMD patients are usually wheelchair bound by age 15 and die from respiratory insufficiency or cardiac decompensation in early adulthood; BMD progresses at a slower but variable rate and have a mildly shortened or normal lifespan
What are the three primary congenital myopathies?
Central core disease, nemaline myopathy, and centronuclear myopathy
