Myositis

Question 1

Myositis : Types and definition

Answer 1

1. Polymyositis and dermatomyositis are autoimmune disorders causing muscle inflammation (myositis).
2. Both present with proximal muscle weakness.

Question 2

Dermatomyositis : Definition

Answer 2

Dermatomyositis also involves characteristic skin changes, specifically

1. Gottron papules affecting the backs of the hands and
2. heliotrope rash affecting the eyelids.

Question 2

Myositis : Pathophysiology

Answer 2

1. Autoimmune response to healthy muscle tissue
2. Inflammatory respone

• T cells infiltrate muscle tissue
• Damage muscle fibres

3 . Muscle fiber degeration

Question 3

Myositis : Causes

Answer 3

1. Secondary to paraneoplastic syndrome
   * Ovarian, Breast and Lung cancer

2 . Viral infection
* HIV
* Coxsackie virus

Question 4

Myositis : Incidence

Answer 4

Women 50-70

Question 5

Myositis : Clinical features

Answer 5

Onset : Gradual

1 . Muscle weakness
* Symmetrical
* Proximal muscle - closest to the trunk ie, Hips, thighs, shoulders, upper arms

2 . Myalgia - muscle pain/tenderness

Dermomyositis skin changes;
1. * *Gottron lesions_ (scaly erythematous patches) on the knuckles, elbows and knees
2. _Heliotrope rash_ (a purple rash on the face and eyelids)
3. * _Periorbital oedema (swelling around the eyes)
4. *Photosensitive erythematous rash* on the back, shoulders and neck

Question 6

Myositis : Investigation

Answer 6

1. Creatine kinase : very high
2. Auto antibodies :
3. Majority are ANA antibody +
   * anti-Jo-1 antibodies :
   Polymyositis.
   Targets enzymes involved in protein synthesis associated
   * Anti Mi 2 : Dermomyositis

Question 7

Myositis : Management

Answer 7

1. first-line treatment : Corticosteroids

Other medical options where the response to steroids is inadequate:

2. Immunosuppressants (e.g., methotrexate or azathioprine)
3. IV immunoglobulins
4. Biological therapy (e.g., infliximab or etanercept)