Week 12: Myositis, Myalgia

Question 1

Pathophysiology of polymyositis

Answer 1

Cytotoxic T cells attack self Ag (not known which Ag) resulting in myositis

Question 2

Pathophysiology of dermatomyositis

Answer 2

Humorally-mediated inflammation of blood vessels resulting in myositis and typical dermatitis

Question 3

Difference between polymyositis and dermatomyositis

Answer 3

Polymyositis only affects muscles.

Dermatomyositis affects muscles and skin

Question 4

Which muscles are affected in polymyositis

Answer 4

Proximal muscles

but ocular muscles are often normal

Question 5

Important complication of polymyositis

Answer 5

Muscle weakness can start to involve respiratory and pharyngeal muscles (can be life threatening)

Question 6

Important complication of dermatomyositis

Answer 6

Strong association with solid organ cancer

Question 7

Skin features of dermatomyositis

Answer 7

1. Photosensitive distribution rash
2. Heliotrope rash over eyelids and cheeks
3. Gottren’s papules (raised lichenoid papules over MCP, DIP, PIP)

Question 8

Diagnostic test in polymyositis/ dermatomyositis

Answer 8

Muscle biopsy

Question 9

Name some causes of periorbital oedema

Answer 9

• Dermatomyositis

- Graves disease

Question 10

How to differentiate myalgia vs myositis in symptoms

Answer 10

Myalgia: muscle pain without weakness

Myositis: muscle weakness +/- pain

Question 11

How to differentiate myalgia vs myositis in blood tests

Answer 11

Myositis will cause raised CK

Myalgia will have normal CK

Question 12

Steroid myopathy is an important differential for myositis.

What occurs during this?

Answer 12

• Proximal muscle weakness
• Fat atrophy

occurs with prolonged high dose steroid use

Question 13

What type of contraception should be avoided in women with antiphospholipid syndrome? Why?

Answer 13

Oestrogen-containing contraception

Due to increased DVT risk

Question 14

What type of rash occurs in dermatomyositis

Answer 14

Heliotrope/ Photosensitive/ Lichenoid rash

Question 15

How are liver enzymes affected in polymyalgia rheumatica

Answer 15

Raised GGT and raised ALP

Question 16

Clinical features of fibromyalgia

Answer 16

FIBRO

Fatigue
Insomnia
Blues (depression)
Rigidity
Ow (pain)

Question 17

Which cancers is dermatomyositis associated with

Answer 17

1. Lung cancer (SCLC, NSCLC)
2. Breast
3. Ovarian
4. Upper 1/3 gut cancer

Question 18

Where do Gottren’s papules tend to be located?

What are they associated with

Answer 18

Extensor tendons of hands

Dermatomyositis