Inflammatory Myopathy

Question 1

Inflammatory myopathy in general

Answer 1

All result in progressive muscle weakness

Inflammatory process in muscle and maybe other places

Question 2

Epidemiology

Dermatomyositis
Polymyositis
Inclusion body myositis

Answer 2

PM - 40-50 and women
DM - any age and more women
IBM - over 50 and more in men

Question 3

Dermatomyositis patho

Answer 3

Autoimmune process

Humoral predominates and autoAbs that activate complement

Inflammation around endomysial capillaries…mostly B, T, and CD4s

Complement triggers ischmemia and micro-infarcts of muscle group

Inflammation around BVs, fibers in perifascicular areas atrophy most

Question 4

Rashes of DM

Answer 4

Helitrope - blue purple discoloration of the upper eyelids with edema

Gotrron-s - erythematous or violaceous macs and paps on extensors of joints

Facial erythema - midface erythema involving malar and nasolabial folds

V sign - erythematous on neck and ant chest

Question 5

DM other CM

Answer 5

Muscle weakness but over months

Wekaness symmetric and in proximal…specifically hip fleoxrs and dletoids

Maybe difficulty climbimg or lifting objects

10% will have lung dz

More likely to be diagnosed with scleorderma or mixed conn tissue dz or malignancy

Question 6

Dx of DM

Answer 6

CK and aldolase elevation
Correlation between elevation and severity

ANA in 80%
Anti-Jo-1, anti-Mi-2 or anti-SRP also more specific

Ultimately, muscle bipsy can establish a def diagnosis demonstrating perivascular inflammation and perifascicular atrophy

Question 7

Management of DM

Answer 7

Goal to reduce weakness

Initial is high dose GC for about a month and tapered

May need azathioprine, mycophenolate or methotrexate

Skin can be tx with GCs or immunosuppressive

Question 8

PM patho

Answer 8

T cell toxicity

CD8s and macros destory healthy muscle tissue

Muscle fibers abberrantly express MHC class 1

In contrast ot DM, lymphocytes predominate around individual muscle fibers and reuslt in myfiber necrosis

Question 9

CM of PM

Answer 9

Insidious muscle weakness

Symmetric proximal weakness of hip flexors and deltoids

Associated with RA, Sjogren’s, and SLE in addition

Not associated with malignancy but may have lung dz

Question 10

Dx of PM

Answer 10

Elevated CK and aldolase

Same as DM except patho shows endomysial inflammation and myofiber necrosis

Question 11

Management of PM

Answer 11

GCs high dose 1st line

May need azathioprine, mycophenolate, or methotrexate

Question 12

IBM patho

Answer 12

Both autoimmune and degenerative

T cell cytotoxicty predominantes due to muscle fiber MHC 1 aberrant expression

Upregulation of MHC 1 leads to intracellular deposition of amyliod and vacuolization….charactieristic of degen process

Question 13

CM of IBM

Answer 13

Years of progression

Proximal muscle weakness is most common but Asymmertic

Distal muscle weakness is universal…ankle dorsiflexion, forearm flexion, deep finger flexion

Dysphagia in 60% and leads to choking

Myscle atrophy and diminished reflexes as well

Atrophy of quads, foot flexors and/or forearms typical

20% have another acollagen vascular dz

Question 14

Dx of IBM

Answer 14

Normal to mildly evelated CK and aldolase

Autoantibodies typically negative

Muscle can confirm with endomysial inflammation, dengen and regen myofibers, and rimmed vacuoles in cytoplasmic inlcusons

Question 15

Managment of IBM

Answer 15

Very difficult to tx…you can try but might not work

PT, OT, ST