Soft Tissue Pathology Flashcards
What are the 2 main groups of muscle pathologies?
Primary
Secondary to nerve damage
How may creatine kinase levels indicate muscle pathology?
High - dystrophy: 200-300 ULN
Intermediate - inflammatory: 20-30 ULN
Low - neurogenic: 2-5xULN
How may histology/biopsy indicate muscle pathology? [5]
Inflammatory markers Cell morphology Necrosis Atrophy Stains/techniques to isolate specific fibres
What are “dystrophic changes” as applied to muscles?
Severe and stereotyped combination of myopathic changes in muscles seen on histology
List 9 dystrophic changes
Variability in muscle fibre size Endomysial fibrosis Fatty infiltration and replacement Myocyte hypertrophy Fibre splitting Increased central nuclei Segmental necrosis Regeneration Ring fibres
List the 4 pathological features common to muscular dystrophies
Destruction of single fibres
Prolonged
Regeneration
Fibrosis
How does Duchenne Muscular Dystrophy present?
Proximal limb weakness
Pseudohypertrophy of calves
Raised CK
At what age does DMD present?
2-4
late onset of walking in boys
dead by 20
Which gene carries a mutation in DMD?
Dystrophin gene, chromosome X
- uncontrolled entry of Ca++ into cells, fibres liable to tears
How does DMD appear on histology? [4]
Muscle fibre necrosis + phagocytosis
Regeneration
Chronic inflammation + fibrosis
Hypertrophy
How does Becker Muscular Dystrophy present?
- variant of DMD
Later onset
Slower progress
- 2 types, DM1 and DM2
How does myotonic dystrophy present?
Muscular weakness Myotonia Non-muscle features - cataracts - heart defects
Which genes are involved in the inheritance of myotonic dystrophy?
Chromosomes 19 and 3
- autosomal dominant
What sites are frequently affected in adolescent-onset myotonic dystrophy?
Face
Distal limbs
What sites are frequently affected in later-onset myotonic dystrophy?
Respiratory muscles
How does myotonic dystrophy appear on histology? [5]
Atrophy of type I fibres Central nuclei Ring fibres Fibre necrosis Fibrofatty replacement
List 3 possible causes of primary inflammation of a muscle
Infection
Polymyositis
Dermatomyositis
Define neurogenic disorders of muscle
Stereotyped muscle changes after nerve damage with subsequent re-innervation
List 4 examples of neurogenic disorders of muscle
Motor neurone disease
Spinal muscular atrophy
Peripheral neuropathies
Misc. spinal disorders
How do neurogenic disorders of muscle appear on biopsy? [5]
Angulated muscle fibres (adults) Rounded muscle fibres (infants) Target fibres Fibre-type grouping Grouped atrophy
What is motor neurone disease?
Progressive degeneration of anterior horn cells
Leads to denervation atrophy, fasciculation and weakness
What is spinal muscular atrophy?
Inherited (autosomal recessive, Ch5)
Degeneration of anterior horn cells -> denervation
Have 4 types
What is myasthenia gravis?
Autoimmune, affects women 20-40yo
Weakness, fatigue and dysphagia
25% have thymoma, others - thymic hyperplasia
What is rhabdomyolysis?
Breakdown of skeletal muscle
What are the 3 systemic consequences of rhabdomyolysis?
- myoglobinuria (renal failure)
- hyperkalaemia -> metabolic acidosis
- necrosis and shock
