Myopathies are primary muscle diseases that cause chronic muscle weakness. There are three broad groups: hereditary myopathies like muscular dystrophies, inflammatory myopathies such as polymyositis and dermatomyositis, and toxic myopathies caused by things like drugs and thyroid disorders. Duchenne muscular dystrophy is the most common and serious hereditary myopathy. It is an X-linked recessive disorder caused by a lack of the dystrophin protein, leading to muscle degeneration. Boys experience progressive muscle weakness starting in early childhood and death usually occurs in late teens. Polymyositis and dermatomyositis are inflammatory myopathies characterized by muscle pain, weakness

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