muscular atrophy: can be generalized, as in prolonged bedrest, or localized, as in immobilization of a body part with a cast. neurogenic atrophy is muscle atrophy that is due to the lack of innervation of muscle fibers, which then necrose-- and can be mixed in next to healthy muscle fibers. neurogenic atrophy might result in contracture due to the reduced resistance of opposing muscle groups.
congenital myopathies are genetic disorders of muscle that present early on and have an insidious progression. they result in general muscle weakness and might have a connection with diet, as elucidated in "breaking the vicious cycle", which describes a possible connection between muscle weakness and intake of simple carbohydrates. duchenne's is one of many types of muscle dystrophy which develops early on and is generally fatal by the 20's. it results from an x linked genetic defect which leads to an absence of dystrophin, a component of the membrane of skeletal muscle. this leads to dysfunctional membrane permeability, which leads to excess calcium levels, cloudy swelling, and ultimately cell death.
myasthenia gravis is an autoimmune neuromuscular condition that results from antibodies to the acetylcholine receptors in neuromuscular junctions. the hallmark symptom is muscle weakness that is worse with activity and better with rest. there is also a strong association with thymic abnormalities, such as hyperplasia or thymomas. histomorphology includes large clusters of lymphocytes and pale / atrophic muscle fibers.
lambert-eaton syndrome is another autoimmune neuromuscular condition in which antibodies to the presynaptic calcium channels are produced, leading to decreased acetylcholine release. it is strongly associated with lung cancer-- in particular oat cell cancer of the lung, and generally appears first on the upper legs and upper arms. diagnosis is made by antibody tests, nerve stimulation tests, and chest xray to detect lung cancer. in contrast to MG, patients with LES might experience greater strength in the beginning of a mild exertion.
dermatositis is an idiopathic inflammatory connective tissue disorder which also has skin and muscle involvement. half of cases are associated with paraneoplastic syndrome. histomorphological signs include perivascular inflammatory infiltrate of mixed B and T cells, and perifascicular musclar atrophy. characteristic signs and symptoms include neck extensor weakness, periorbital heliotrope rash, grotton's sign (purple/red papular rash on the dorsal side of fingers).
questions
muscular atrophy...
1. what might cause generalized vs. localized atrophy?
2. what might atrophy be masked by?
3. what is neurogenic atrophy?
4. describe the morphology of neurogenic atrophy.
5. neurogenic atrophy might result in...
congenital myopathies...
6. describe the onset and course of most congenital myopathies.
7. what is a diet that might have a connection with muscle tone and what is the book in which these findings were presented?
8. what are the signs / symptoms of congenital myopathies?
muscle dystrophies...
9. how many forms of muscle dystrophies are there? which is most common?
10. muscular dystrophies are characterized by...
11. what is the etiology of duchenne's?
12. which gender is associated with duchenne's?
13. describe the pathophysiology of duchenne's.
14. what is the typical age of onset for duchenne's?
15. describe the distribution of duchenne's.
16. what is "pseudohypertrophy"?
17. describe the histomorphology of the early and late stages of duchenne's.
18. what is the prognosis of duchenne's?
myasthenia gravis...
19. what is the etiology of myasthenia gravis?
20. what is the hallmark symptom of MG?
21. there is an association between MG and...
22. what is the histomorphology of MG?
23. how is diagnosis of MG made?
lambert-eaton syndrome...
24. where is LES first noticed?
25. 60% associated with...
26. what is the etiology of LES?
27. describe the symptom picture of patients with LES.
28. how is LES diagnosed?
dermatositis...
29. what is dermatositis?
30. what is the etiology of dermatositis?
31. besides muscle weakness, how is dermatositis diagnosed?
32. what are the 2 characteristic histomorphological signs of dermatositis?
33. what are the characterizing signs/symptoms of dermatositis?
34. what is grotton's sign?
polymyositis...
35. what is the main difference between polymyositis and dermatositis?
36. which muscles are affected in polymyositis?
37. what is a sign that occurs in 1/3 of patients that indicates poor prognosis?
38. what is a common presentation of a patient with polymyositis?
39. what is the histomorphology of polymyositis?
40. describe the composition of the inflammatory infiltrate in polymyositis.
answers
1. generalized: lying in bed for a long time. localized: wearing a cast.
2. fat deposition in between muscle fibers.
3. muscle atrophy as a result of decreased nerve supply.
4. areas of atrophied tissue mixed with healthy tissue.
5. contractures due to reduced resistance in opposing muscle groups.
6. generally early onset and gradual progression.
7. specific carb diet, in "breaking the vicious cycle".
8. generalized or proximal muscle weakness, hypotonia.
9. hundred's, duchenne's.
10. progressive skeletal muscle weakness.
11. defective gene on X chromosome that leads to inability to produce dystrophin, a skeletal muscle membrane protein.
12. almost exclusively in boys.
13. absence of dystrophin leads to membrane permeability changes which leads excess calcium and ROS, cloudy swelling and ultimately to cell death.
14. 2-6yo.
15. proximal large muscles and spreads to all voluntary muscles.
16. muscle that is replaced by fat and thus appears to be hypertrophied.
17. early: scattered inflammatory cells. late: pseudohypertrophy.
18. wheelchair bound by age 12, generally fatal by 20's.
19. autoimmune condition in which antibodies are produced against the acetylcholine receptors at the neuromuscular junctions, resulting in an inhibition of acetyl choline's stimulatory activity.
20. muscular weakness that worsens with activity and improves with rest.
21. thymic abnormalities such as thymic hyperplasia.
22. large collections of lymphocytes, and pale/atrophic necrotic muscle fibers.
23. history, PE, and two positive diagnostic tests: serum antibodies, nerve stimulation studies, tensilon injection studies.
24. upper legs/upper arms.
25. oat cell cancer of the lung.
26. antibodies to the presynaptic calcium channels, resulting in inhibition of Ach release.
27. greater strength with initial exertion but weakness upon prolonged exertion.
28. chest x ray for lung involvement, antibody tests, nerve conduction studies.
29. connective tissue disease with muscle and skin involvement.
30. unknown, although 50% have an association with paraneoplastic syndrome.
31. skin involvement, elevated CPK, ESR, EMG, and muscle biopsy.
32. mixed B/T cell perivascular inflammatory infiltrate and perifascicular muscle atrophy.
33. neck extensor weakness
dysphagia / aspiration
periorbital heliotrope rash
grotton's sign
34. symmetrical purple/red papular rash over dorsal aspect of finger joints.
35. no skin involvement in polymyositis.
36. symmetric proximal muscles, especially neck flexors.
37. oropharyngeal and esophageal involvement.
38. inability to rise from a seated position.
39. pale and enlarged muscle fibers, surrounded by macrophages.
40. cytotoxic T8 lymphocytes.
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