Seminar G Dermatomyositis and Polymyositis

Question 1

Definition

Answer 1

Polymyositis is an autoimmune disease characterised by inflammation of striated muscle.

Question 2

Epi

Answer 2

2-10 per million/yr

Question 3

Female:Male

Answer 3

2.5:1

Question 4

Peak mean ages

Answer 4

Childhood and 40-50 years

Question 5

Aetiology and Pathogenesis

Answer 5

Associations with HLA-DR3 and Drw52

First degree relatives

Question 6

Environmental factors

Answer 6

More common in winter and spring
Influenxa
Coxsackie
Echo

Question 7

Drug induced myositis

Answer 7

HMG-CoA reductase inhibitors (Statins)
D-penicillamine
Chloroquine

Question 8

Hallmark Feature

Answer 8

Painless proximal muscle weakness

Question 9

More advanced disease

Answer 9

Pharyngeal musculature result difficulty in initiating swallowing, whilst exertional dyspnoea may result from respiratory muscle weakness.

Question 10

MRC motor scale

Answer 10

May be used to record muscle power

Question 11

Blood tests

Answer 11

Acute phase response, with a raised ESR or plasma viscosity
Anaemia
Muscle enzymes will be grossly elevated, as they leak from damaged skeletal muscle.

Question 12

Creatine Kinase (CK)

Answer 12

Most sensitive and best guide to muscle inflammation, but other enzymes such as lactate dehydrogenase, and the transaminases (ALT and AST) may

Question 13

Autoimmune profile may show

Answer 13

Positive Antinuclear (ANA) and anti-Jo-1 antibodies may also be present.
An electromyogram

Question 14

Treatment → Symptoms

Answer 14

Oral prednisolone

Question 15

Treatment → Other Agents

Answer 15

Azathioprine

Methotrexate

Question 16

Treatment → Prevent glucocorticoid-induced osteoporosis

Answer 16

Bisphosphonates

Question 17

Association with Malignancy →
Underlying neoplastic lesions seen in 10-15% of cases in the first 6 months.
Examples:

Answer 17

1. Adenocarcinoma of the colon
2. Prostatic carcinoma
3. Ovarian tumours
4. Breast cancers