Dermatomyositis

Question 1

What is dermatomyositis?

Answer 1

An inflammatory disorder causing symmetrical, proximal muscle weakness and characteristic skin lesions.

Question 2

What can this be associated with?

Answer 2

Can be idiopathic or may be idiopathic or associated with connective tissue disorders or underlying malignancy (typically ovarian, breast and lung cancer, found in 20-25% - more if patient older)

Question 3

What is usually performed following a diagnosis of dermatomyositis?

Answer 3

Screening for an underlying malignancy

Question 4

What is a variant of the disease where skin manifestations are not prominent?

Answer 4

Polymyositis

Question 5

Skin features?

Answer 5

• photosensitive
• macular rash over back and shoulder
• heliotrope rash in the periorbital region
• Gottron’s papules - roughened red papules over extensor surfaces of fingers
• ‘mechanic’s hands’: extremely dry and scaly hands with linear ‘cracks’ on the palmar and lateral aspects of the fingers
• nail fold capillary dilatation

Question 6

Other features?

Answer 6

• proximal muscle weakness +/- tenderness
• Raynaud’s
• respiratory muscle weakness
• interstitial lung disease: e.g. Fibrosing alveolitis or organising pneumonia
• dysphagia, dysphonia

Question 7

How many patients are ANA positive?

Answer 7

Majority of patients (80%) are ANA positive

Question 8

How many patients have anti-synthetase antibodies?

Answer 8

Around 30%

Question 9

What anti-synthetase antibodies can be found?

Answer 9

o antibodies against histidine-tRNA ligase (also called Jo-1)
o antibodies to signal recognition particle (SRP)
o anti-Mi-2 antibodies