Skeletal Muscle Disease

Question 1

What is dermatomyositis and what is the cause of it?

Answer 1

Inflammation of the skin and muscle. Etiology is unknown, but some cases are associated with carcinoma, especially gastric.

Question 2

4 clinical features of dermatomyositis?

Answer 2

Bilateral proximal muscle weakness
Purple rash of the upper eyelids
Male rash (don’t get confused with lupus)
Red papules on knees, elbows and knuckles

Question 3

2 lab findings of dermatomyositis and what do we see on biopsy?

Answer 3

Increased Creatine Kinase
Positive ANA and Anti Jo1 antibody

Perimysial inflammation with perifascicular atrophy

Question 4

How do we treat dermatomyositis?

Answer 4

Corticosteroids

Question 5

What is polymyositis and what are 3 differences between it and dermatomyositis?

Answer 5

Inflammatory condition of skeletal muscle
Does not involve the skin
Endomysial inflammation
Necrotic muscle fibers seen on biopsy

Question 6

What is the problem with duchesse muscular dystrophy?
What is the biochemical cause?
How does it classically present?
What is a characteristic finding?
What is a lab value associated with it?
What do these patients die from?

Answer 6

Muscle wasting/weakness with replacement of the muscle with fat
Deletion of dystrophin
Proximal muscle weakness at 1 year of age, which will progress to distal musculature
Pseudo calf muscle hypertrophy
Elevated CK
Cardiac or respiratory failure

Question 7

How is Becker muscular dystrophy different?

Answer 7

It is a mutation in dystrophin, not deletion, so the disease is more mild.