Dermatomyositis/ Polymyositis

Question 1

What is polymyositis?

Answer 1

An autoimmune condition that causes progressive muscular weakness that is associated with muscle pain

Question 2

What is dermatomyositis?

Answer 2

Dermatomyositis is polymyositis with skin involvemement

Question 3

What skin signs are seen in dermatomyositis?

Answer 3

Gottron’s Papules- rouge red papules over the knuckles but also knees and elbows

Heliotrope Rash- Purplish rash around the eyes

Macular rash over back and shoulders

Question 4

What are the problems that may be causes by polymyositis/dermatomyositis?

Answer 4

Progressive muscle weakness may lead to:
Cardiomyopathy
Aspiration Pneumonia
Reduced ventilation
Increased falls risk

Question 5

What are some extra-muscular/skin signs of polymyositis/dermatomyositis?

Answer 5

Generally- Lethargy, fatigue, weight loss

Arthralgia
Raynaud’s
Interstitial Lung disease

Question 6

What antibodies are associated with polymyositis/dermatomyositis?

Answer 6

ANA

Anti JO2
Anti M2

Question 7

What investigations could you do if suspecting polymyositis/dermatomyositis?

Answer 7

Immunology- ANA, Anti JO2, Anti M2

Muscle Enzymes- CK, Myoglobin, LDG, ALT, AST

EMG- characteristic fibrillation potentials

Muscle Biopsy (confirms diagnosis)

MRU Imaging- may show oedema in acute myositis

Question 8

What is the management for polymyositis/dermatomyositis?

Answer 8

Immunosuppression

Steroids and steroid sparing agents

Question 9

Importantly, what could polymyositis or dermatomyositis be a sign of?

Answer 9

Underlying malignancy as it can be a paraneoplastic phenomenon