PMDM - finished

Question 1

Define polymyositis and dermatomyotisis

Answer 1

A multi-system connective tissue disease characterised by inflammation and degeneration in the muscles (polymyositis), and the muscles + skin (dermatomyotisis) leading to symmetric weakness and some degree of muscle atrophy

Question 2

Aetiology of DM and PM

Answer 2

idiopathis however some evidence for autoimmune and viral causes

Autoimmune:

• IgM, IgG and complement deposits are seen in the walls of skeletal muscle blood vessels
• ANA’s present
• signs of cell mediated immune reaction to muscle

Viral:
- virus like structures have been found in affected cells

Question 3

Epidemiology of PMDM

Answer 3

F:M = 2:1
Commonly seen in:
- adults 40-60 (insidious)
- kids 5-15 (acute)

Question 4

Pathology of PMDM

Answer 4

Skin changes:

• secondary to immune mediated vasculitis and inflam. occuring at the interface between dermis and epidermis
• results in:
  
  • epidermal atrophy
  • basal cell liquefaction
  • vascular dilation
  • lymphocytic infiltration of dermis

Muscle changes: (myositis)

• Caused by chronic T-cell infiltration:
• results in:
  
  • necrosis
  • phagocytosis
  • regenerative activity
  • atrophy and degeneration of muscle tissue
  • increased connective tissue content

Question 5

What are the initial manifestations of PMDM?

Answer 5

Proximal muscle weakness
Muscle tenderness and pain
Skin rash
Polyarthralgia
Raynauds phenomenon
Dysphagia
Systemic ssx

Question 6

What are the typical clinical manifestations of PMDM?

Answer 6

Proximal muscle weakness: 100% cases
Cutaneous eruption
Polyarthralgia: 33% cases
Raynaud phenomenon
Visceral involvement

Question 7

What are the ssx of cutaneous eruption in PMDM??

Answer 7

Is due to vasculitis.

• dusky erythematous rash over chest and neck
• • • gottrons papules: when the rash is slightly elevated and is smooth or scaly (eg over knuckles)
• • • heliotrope rash: periorbital purple skin discolouration

** pathognomonic

Question 8

What are the ssx of polyarthralgia in PMDM?

Answer 8

Mild
Usually see:
- swelling
- joint effusion
- raynauds phenomenon

Question 9

What are the ssx of visceral involvement in PMDM?

Answer 9

Uncommon
Usually see:
- interstitial pneumonitis
- cardiac involvement
- acute renal failure (due to rhabdo)
- sjogrens syndrome
- malignancy in 15% cases, usually carcinoma of breast, GIT and bronchus

Question 10

Lab findings for PMDM?

Answer 10

• increased ESR
• increased serum muscle enzymes
• 80% have ANA’s (myositis specific antibodies in 50% patients with ANA’s)

Question 11

Diagnostic criteria for PMDM:

Answer 11

1: Skin lesions
2: Prox. muscle weakness
3: Increased serum muscle enzymes (e.g.CK)
4: Muscle pain
5: Characteristic EMG changes
6: Anti RNA Ab’s
7: Non-destructive arthritis
8: Systemic inflammation (e.g. fever and raised ESR)
9: Muscle biopsy

Pts with at least one finding from item 4 and 4 findings from items 2-9 have dermaomyositis

Pts with 4 findings from items 2-9 have polymyositis