Pathology Flashcards
Describe type 1 muscle fibres
Red, large mitochondria and increased myoglobin
Describe type 2 muscle fibres
White, small mitochondria & large motor end plates
What are some indications for performing a muscle biopsy?
Evidence of muscle disease-weakness, atrophy, fasciculation, elevated CK, presence of neuropathy (+nerve biopsy), presence of vascular disorder (vasculitis)
Describe high, medium and low CK levels
High: 200-300x normal (dystrophies). Medium:20-30x (inflammatory myopathy). Low : 2-5x (neurogenic disorder)
Describe some dystrophic changes in histology
Variability in muscle fibre size, endomysial fibrosis, fatty infiltration and replacement, myocyte hypertrophy & fibre splitting, increased central nuclei, segmental necrosis, regeneration, ring fibres
What occurs to muscles and CK in DMD?
Proximal weakness, pseudohypertrophy of calves. Raised CK
What mutation occurs in DMD?
Mutations in dystrophin gene on long arm of ChX
What changes occur regarding cell structures in DMD?
Alterations in anchorage of actin cytoskeleton to basement membrane. Fibres liable to tearing, uncontrolled Ca2+ entry
What histological changes occur in DMD?
Muscle fibre necrosis & phagocytosis
Regeneration
Chronic inflammation and fibrosis
Hypertrophy
Describe the onset, mutation and progress of BMD
Later onset, mutation in dystrophin (like DMD), slower progress
What are the most common types of myotonic dystrophy?
DM1 (distal), DM2(proximal)
What symptons occur in myotonic dystrophy?
Muscle weakness, myotonia, non-muscle features- cataracts, frontal baldness in men, cardiomyopathy, low intelligence
What inheritance occurs in myotonic dystrophy?
Autosomal dominant-Ch19/3
What areas are affected by myotonic dystrophy?
Adolescence- face, distal limbs. Later-respiratory muscles
What histological changes occur in myotonic dystrophy?
Atrophy of type 1 fibres, central nuclei, ring fibres, fibre necrosis, fibrofatty replacement
What is polymyositis?
Cell-mediated immune response to muscle antigens
What pathological changes occur in polymyositis?
Endomysial lymphocytic infiltrate, invasion of muscle by CD8+ T cells, segmental fibre necrosis
What is the difference between dermatomyositis and polymyositis?
Dermatomyositis is polymyositis plus skin changes
What changes occur in dermatomyositis?
Upper body erythema, swelling of eyelids with purple discolouration
What are the pathological changes that occur indermatomyositis?
Immune complex and complement deposition within and around capillaries within muscle. Perifascicular muscle fibre injury. B-cells/CD4+ T cells > polymyositis
What is MND?
Progressive degeneration of anterior horn cells. Denervation atrophy, fasciculation and weakness
What is the genetic mutation behind spinal muscular atrophy?
Inherited autosomal recessive-Ch5
What occurs in spinal muscular atrophy?
Degeneration of anterior horn cells in spinal cord, and denervation of muscle
What type of disorder is Myasthenia Gravis?
Autoimmune
What symptoms occur in Myasthenia Gravis?
Weakness, proptosis, fatigue and dysphagia
Who does myasthenia gravis commonly effect?
Women between 20-40
What percentage of people with Myasthenia Gravis have thymoma, and what may others have alternatively?
25%- others may have thymic hyperplasia
What is Rhabdomyolysis, and what occurs systemically?
Breakdown of skeletal muscle- myoglobinuria, hyperkalaemia, necrosis and shock
What is the outcome of rhabdomyolysis?
Acute renal failure, hypovolaemia, hyperkalaemia, metabolic acidosis, disseminated intravascular coagulation
What is SLE?
AI multisystem disorder, involving ANA’s, has genetic factors and may be drug induced (hydralazine and pracainamide). F-M 9:1
What symptoms/conditions occur as a result of SLE?
Butterfly rash, discoid lupus erythematosus (DLE), arthralgia, glomerulonephritis, psychiatric symptoms, focal neurological symptoms, peri/myocarditis, necrotizing vasculitis, lymphadenopathy, splenomegaly, pleuritis, pleural effusions, anaemia, leucopenia, thrombophilia
What hypersensitivity presentations occur in SLE?
Visceral lesions (Type III), Haematological effects (Type II)
What is polyarteritis nodosa (PAN)?
Inflammation and fibrinoid necrosis of small/medium arteries?
What is the aetiology of PAN?
Unknown
What are the target organs of PAN?
Kidneys, heart, liver, GI tract, skin, joints, muscles, nerves, lungs
What are the clinical features of PAN?
Non-specific +/- organ specific features- HT, haematuria, abdo pain, melaena, diarrhea, mononeuritis multiplex, rash, cough, dyspnoea
How is PAN diagnosed?
Biopsy; fibrinoid necrosis of vessels. Serum contains pANCA (perinuclar antineutrophil cytoplasmic autoantibody)
How does polymyalgia rheumatica present?
In elderly commonly- pain, stiffness in shoulder & pelvic girdles. No muscle weakness
What is Temporal arteritis?
Inflammation affecting cranial vessels.
What are the symptoms of temporal arteritis?
Headache and scalp tenderness. Risk of blindness if terminal branches of ophthalmic artery affected
How is temporal arteritis diagnosed?
Raised ESR- temporal artery biopsy; inflammation, +/- giant cells, fragmentation of internal elastic lamina
What is scleroderma?
Excessive fibrosis of organs and tissues (excessive collagen production)
What symptoms/conditions occur due to scleroderma?
Skin is tight, tethered, decreased joint movement. GIT-fibrous replacement of muscularis. Pericarditis and myocardial fibrosis. Interstitial fibrosis. Kidneys-affects arteries > HT, MSK- polyarteritis and myositis
What syndrome is scleroderma associated with?
CREST
