Poly/Dermatomyositis

Question 1

aetiology of poly/dermatomyositis

Answer 1

rare condition
insidious onset of progressive symmetrical proximal muscle weakness
usually due to AI-mediated striated muscle inflammation
often paraneoplastic (esp. derm)

Question 2

what is polymyositis

Answer 2

endomysial inflammation with CD8+ t cells
most often involves shoulders

Question 3

what is dermatomyositis

Answer 3

perimysial inflammation with CD4+ t cells
MAC causes destruction

Question 4

presentation of polymyositis

Answer 4

progressive symmetrical muscle weakness

Question 5

typical presentation of dermatomyositis

Answer 5

progressive symmetrical muscle weakness AND

gottron’s papules
facial erythema
shawl rash
mechanic’s hands
nail fold capillary dilatation

Question 6

what are gottron’s papules in dermatomyositis

Answer 6

rough, red papules across knuckles, knees, elbows

Question 7

what facial erythema can be seen in dermatomyositis

Answer 7

heliotrope rash: violaceous or dusky red rash surrounding the eye.

can affect one or both eyes

is sometimes associated with periorbital oedema

Question 8

what is shawl rash

Answer 8

darkening of shoulders and chest

Question 9

ix of poly/dermatomyositis

Answer 9

muscle enzymes: ck and aldolase
EMG: fibrillation potentials
muscle biopsy (confirms)
auto-ab (anti-synthetase antibodies): anti-SRP, anti-Mi2, anti-jo1 (80% are ANA+)

Question 10

what is jo1?

Answer 10

tRNA synthetase a/w interstitial fibrosis

Question 11

mx of poly/dermatomyositis?

Answer 11

corticosteroids

Question 12

comps of poly/dermatomyositis?

Answer 12

coricosteroid effects

Question 13

what forms part of a malignancy screen in dermatomyositis?

Answer 13

lung, breast, ovarian, prostate, colorectal
- CXR
- FOBT
- mammography
- CA125
- PSA (in m ales)
- pelvic ultrasound (in females)
- potentially CT CAP
- basic bloods - serum corrected calcium, LFTs (bone and liver metastases)

Question 14

what are mechanic’s hands?

Answer 14

extremely dry and scaly hands with linear ‘cracks’ on palmar and lateral aspects of fingers

Question 15

other features of dermatomyositis?

Answer 15

raynaud’s
resp muscle weakness
ILD (e.g. fibrosing alveolitis, organising pneumonia)
dysphagia, dysphonia

Question 16

gottron’s sign vs gottron’s papules?

Answer 16

gottron’s sign: violaceous macules, sometimes with associated oedema, over the knees and elbows.

gottron’s papules: small violaceous papules, often seen on the proximal interphalangeal and metacarpophalangeal joints

both associated with dermatomyositis

Question 17

what is antisynthetase syndrome?

Answer 17

subtype of dermatomyositis
characterised by myositis + ILD
caused by anti-Jo1 ab