Myopathies

1. MYOPATHIES

2. •
Primary muscle disease resulting in
chronic muscle weakness
• 3 broad grps –
1. Hereditary ( muscular dystrophies)
2. Inflammatory –
polymyositis, dermatomyositis
3. Toxic myopathies –
thyrotoxic, ethanol, drug induced

3. Muscular dystrophies
• Grp of genetically inherited primary muscle
disease, progressive muscular weakness

4. Duchenne muscular dystrophy
• Commonest, most serious
Clinical features – muscle weakness in early
childhood, death by late teens
Morphology – muscle fibre necrosis,
regeneration
• Fibres atrophic, fibrosis, fatty replacement

5. Etiology – X linked recessive, boys
• Dystrophin gene lies on the short arm of
chromosome X
• Lack of dystrophin leads to muscle cell
degeneration

6. • Biopsy in early stages show lack of
dystrophin using immunostaining
• Becker type – milder form caused by
mutation in dystrophin gene resulting in
decreased levels of protein
• Other muscular dystrophies – facio
scapulohumoral, limb girdle, myotonic

8. Polymyositis – any age & sex, muscle
pain, weakness, proximal muscle
grps, deterioration rapid / slow
Dermotomyositis – similar with skin lesions
on face & hands
• In adults may herald malignancy –
bronchial CA, CT disorder - RA

9. Pathology
• Muscle fibres show atrophy to necrosis
• Few hypertrophied
• Lymphocytic infiltrate
• Autoimmune etiology

10. Toxic myopathy
• Myopathy seen in
acromegaly, hyperthyroidism, hypothyroidi
sm &
hyperaldosteronism, hyperparathyroidism
& corticosteroid excess

11. • In alcoholics & drug induced - eg
chlroquine, vincristine & vit D def.

12. Diagnosis
- few condition curative therapy is available
• General clinical findings – family
history, age of onset, distribution of muscle
weakness & rate of progress
- neurological assesment

13. • Special investigation of neuromuscular
electrical activity
- rate of motor & sensory nerve conduction
measured electrically
- electromyogram records activity of grp /
individual muscle fibre activity

14. • Lab test
muscle biopsy –
routine, EM, histochemistry
serum enzymes
muscle fibre destruction – CK & aldolase

15. Poliomyeltis
• Poliovirus member of picorna grp of
enteroviruses
• Paralytic poliomyelitis has been effectively
controlled by immunization in many parts
of the world
• Non immunized – infection subclinical /
mild gastroenteritis
• Secondarily invades nervous system

16. CNS infection – initially meningeal irritation
• Progresses to spinal cord
• Attacks ant.horn with loss of motor
neurons produces flaccid paralysis with
wasting & hyporeflexia in affected spinal
segment

17. Acute disease – death may occur due to
paralysis of resp muscles or myocarditis
Morphology
• Acute – mononuclear perivascular cuffs &
neuronophagia of ant horn motor neurons
of spinal cord
• Inflammation can extend to post horns

18. • Post polio syndrome – 25 -35yrs after
resolution of initial illness, progressive
weakness ass.with muscle bulk & pain

19. Volkmann’s contracture
• Young, muscles of forearm
• Ass.with pressure of splints / tourniquet /
with h’ge resulting from #
• Within few hrs after injury pain develops in
hands / forearm -> contractures of fingers
which becomes fixed in flexed position

20. Morphology
• Muscle – hard, homogenous, yellowish
• Nuclei & cross striations are lost
• Inflammatory cells & macrophages at the
margins -> fibrosis
• Cause arterial spasm resulting from injury
to vessel wall