Define the terms:
a. polymyositis
b. dermatomyositis
A multisystem connective tissue disease characterised by inflammatory and degenerative changes in muscles (ie polymyositis) and frequently also in the skin (dermatomyositis) leading to symmetric weakness and some degree of muscular atrophy.
Describe the pathological processes occurring in the skin in dermatomyositis. In your answer explain why these processes is occurring.
• Skin changes → secondary to immune mediated vasculitis and inflammation occurring at the interface between the epidermis and dermis.
• Leads to: o epidermal atrophy o vascular dilation o basal cell liquefaction/degeneration o lymphocytic infiltration of dermis
Describe the pathological processes occurring in muscle in dermatomyositis.
• characterized by direct T cell-mediated muscle injury
- Muscle changes → myositis:
- necrosis
- atrophy and degeneration of muscle fibres
- phagocytosis
- increased connective tissue content
- regenerative activity
Which muscles are affected in dermatomyositis?
Proximal Mm groups.
Describe the typical clinical presentation seen during the onset of dermatomyositis.
- Proximal muscle weakness
- Skin rash
- Polyarthralgia
- Raynaud’s Phenomenon
- Visceral involvement
Describe the key features of the muscle weakness encountered in dermatomyositis.
- symmetrical
- progressive (results in wasting)
- affects proximal muscles in particular
- SSX will depend on which muscles are affected
Describe the characteristic skin rash encountered in dermatomyositis.
Gottran’s Papules
Which skin manifestation is pathognomonic for dermatomyositis?
- periorbital oedema
- heliotrope hue (purplish eyelids)
Why is a thorough clinical evaluation especially important in patients suffering from dermatomyositis?
Malignancy should be considered in any adult with dermatomyositis because the polymyositis usually occurs months or years before the malignancy becomes symptomatic.
