Inflammatory Myopathies

Question 1

What is dermatomyositis?

What is its mechanism?

Answer 1

Autoimmune antibody-mediated vasculopathy leading to muscle damage

Question 2

What are the clinical features of dermatomyositis?

Answer 2

Muscle:

• proximal muscle weakness (bilateral)
• difficulty climbing stairs or raise things with arms

Dermatologic:

• heliotrope rash (periorbital edema w/ purple upper eyelids)
• malar rash
• Gottron papules (erythematous papules on extensor surfaces of hands, elbows, and knees)
• poikiloderma or “shawl sign” (erythema of neck, shoulders, and upper chest/back; area covered by a shawL)

Question 3

What is the epidemiology of dermatomyositis?

Answer 3

• twice as likely in females
• bimodal age distribution; childhood (5-15) and older adults (40-60)

Question 4

What are expected lab and biopsy findings with dermatomyositis?

Answer 4

Lab:

• increased CK/aldolase
• positive ANA (anti-Jo-1 and anti-M2)

Muscle biopsy:

• perifascicular atrophy
• perimysial and perifascicular inflammation (CD4⁺ T cells)
• perimysium is the outer layer and closest to the skin; dermatomyositis has skin involvement

Question 5

What is the treatment/management for dermatomyositis?

Answer 5

-corticosteroids

Question 6

What is an associated condition with dermatomyofibrosis?

Answer 6

malignancy in 15-24% -> paraneoplastic dermatomyositis

Question 7

What are potential complications of dermatomyositis?

Answer 7

• dysphagia (33%)
• interstitial lung disease (10%)
• cardiac involvement is common but cardiac failure is rare

Question 8

What is polymyositis?

What is its mechanism?

Answer 8

Autoimmune cell-mediated condition resulting in muscle damage (vasculature spared compared to dermatomyositis)

Question 9

What are the clinical features of polymyositis?

Answer 9

• proximal muscle weakness (bilateral)
• difficulty climbing stairs or raise things with arms

NO SKIN INVOLVEMENT

Question 10

What is the epidemiology of polymyositis?

Answer 10

• twice as likely in females
• mid to older adults (30-60)
• African American

Question 11

What are expected lab and biopsy findings with polymyositis?

Answer 11

Lab:

• increased CK/aldolase
• positive ANA (anti-Jo-1)

Muscle biopsy:

• necrotic muscle fibers
• endomysial and intrafascicular inflammation (CD8+ T cells)
• endomysium is the inner layer and furthest from skin; polymyositis has no skin involvement

Question 12

What is the treatment/management for polymyositis?

Answer 12

-corticosteroids

Question 13

What is inclusion body myositis?

Answer 13

Autoimmune cell-mediated? inflammatory myopathy

Question 14

What are the clinical features of inclusion body myositis?

Answer 14

Muscle:

-distal muscle and quadriceps weakness (bilateral)

Question 15

What is the epidemiology of inclusion body myositis?

Answer 15

• twice as likely in males
• older adults (>50)
• caucasian

Question 16

What are expected lab and biopsy findings with inclusion body myositis?

Answer 16

Lab:

• increased CK/aldolase
• positive ANA (anti-cN1A)

Muscle biopsy:

• rimmed vacuoles
• endomysial inflammation (CD8+ T cells)