Inflammatory Muscle Pathology

Question 1

Name 3 inflammatory myopathies

Answer 1

• dermatomyostitis
• polymyostitis
• inclusion body myositis

Question 2

Name 4 factors characterize inflammatory myopathies

Answer 2

• presence of inflammatory cells
• necrosis & phagocytosis of m. fibers (>regeneration)
• mixed regenerating & atrophic fibers
• fibrosis

Question 3

What are the common clinical manifestations of inflammatory myopathies?

Answer 3

• symmetrical muscle weakness
• gradual ^symptoms over weeks-months
• progressive difficulty w/ ADLs
• commonly comorbin w/ other autoimmune dz

Question 4

What are the common lab results of inflammatory myopathies?

Answer 4

• ^serum muscle-derived enz. (creatine kinase)
• ^ESR/CRP

Question 5

What are the possible treatments for inflammatory myopathies?

Answer 5

• immunosuppressant drugs (DMARDs) or IV immunoglobulin

Question 6

Which inflammatory myopathy has no effective therapy?

Answer 6

Inclusion body myositis
(can be fatal)

Question 7

What treatment is used diagnostically for inflammatory myopathies based on responsiveness to the treatment?

Answer 7

Corticosteroids (autoimmune is not responsive to this)

Question 8

What age group is primarily affected by Dermatomyositis?

Answer 8

adults > kids

Question 9

What comorbidities are seen with Dermatomyositis?

Answer 9

Systemic sclerosis or other autoimmune disorders

Question 10

What are the clinical manifestations specific to Dermatomyositis?

Answer 10

• rash on upper eyelids, face, upper torso, and/or other areas
• symmetrical proximal muscle weakness

Question 11

What is the etiology of Dermatomyositis?

Answer 11

autoimmune: compliment mediated (humoral immunity)

Question 12

Describe the pathogenesis of Dermatomyositis

Answer 12

• compliment mediated Ab’s attack microvasc. of skeletal m. (angiopathy)
• ischemia of individual m. fibers
• necrosis of skeletal m. tissue & fiber atrophy
• infarct may occur due if large intramuscular aa
  (similar process for other tissues & organs)

Question 13

Why can Dermatomyositis be life threatening?

Answer 13

not limited to skeletal m, can affect other tissues & organs
(eg. respiratory & swallowing problems)

Question 14

What age group is primarily affected by Polymyositis?

Answer 14

> 20 yrs

Question 15

What are the clinical manifestations specific to Polymyositis?

Answer 15

• symmetrical proximal muscle weakness
• NO skin involvement

Question 16

What is the major difference between Polymyositis and Dermatomyositis?

Answer 16

No angiopathy (skin rash) in Polymyositis.
T-cells directly attack m. fibers

Question 17

What is the etiology of Polymyositis?

Answer 17

autoimmune

Question 18

Describe the pathogenesis of Polymyositis

Answer 18

• T-cells attack m. fibers
• necrosis, phagocytosis, regeneration, fibrosis
• systemic progression

Question 19

Polymyositis has similar muscle inflammation to that of ____

Answer 19

HIV infection

Question 20

What is the most common inflammatory myopathy in geriatric patients?

Answer 20

Inclusion body myositis

Question 21

What age group is primarily affected by Inclusion body myositis?

Answer 21

> 50 yrs

Question 22

What is the etiology of Inclusion body myositis?

Answer 22

presence of specific antigen on sarcolemma

Question 23

Describe the pathogenesis of Inclusion body myositis

Answer 23

• specific antigen on sarcolemma
• T-cells attack skeletal m. fiber
• basophilic granular inclusions in cytoplasm or nuclei of involved m. fibers & near vacuoles

Question 24

What muscles are typically involved in Inclusion body myositis?

Answer 24

begins distally (hands & feet)

Question 25

What muscles are typically involved in Dermatomyositis and Polymyositis?

Answer 25

Begins proximally (shoulders, hips, torso)

Question 26

What do inclusions contain in Inclusion body myositis?

Answer 26

• intracellular beta-amyloid plaques, Tau proteins, and other proteins associated with Alzheimer
• Parkin (associated w/ Parkinson dz & prion precursor)