SM_246a: Inflammatory Myopathies

Question 1

Inflammatory myopathies are those where inflammatory response is directed against ____, ____, and ____

Answer 1

Inflammatory myopathies are those where inflammatory response is directed against normal muscle, supporting stroma, and muscle as one of many tissues

(all inflammation in muscle is NOT an autoimmune inflammatory myopathy)

Question 2

Inflammatory myopathies include ____, ____, ____, and ____

Answer 2

Inflammatory myopathies include polymyositis, dermatomyositis, inclusion body myositis, and necrotizing autoimmune myopathy

• Dermatomyositis: adults with skin involvement, juvenile
• Necrotizing autoimmune myopathy: statin induced necrotizing myositis, signal reduction particle myopathy

Question 3

Other sites thay may be involved in inflammatory myopathies are ____, ____, and ____

Answer 3

Other sites thay may be involved in inflammatory myopathies are skin, joint, and lung (ILD)

Question 4

Take muscle biopsy from the ____ area on MRI

Answer 4

Take muscle biopsy from the white area on MRI

Question 5

Describe clinical manifestations of polymyositis

Answer 5

Polymyositis

• Symmetric, proximal greater than distal
• Occasional mild facial weakness
• Can present with dysphagia
• Insidious but not hyperacute
• Myalgias
• Pulmonary involvement
• Anti-Jo-1: female more than male
• Constitutional symptoms including fever weight loss, and myalgias
• Rare myocarditis
• Polyarthralgias

Question 6

Most important test for polymyositis is _____

Answer 6

Most important test for polymyositis is creatine kinase

• Serologic tests: ESR, ANA w/ autoimmune pannel, CRP, myositis antibody painel
• EMG abnormalities but NCS usually ok
• Muscle biopsy

Question 7

Describe pathology of polymyositis

Answer 7

Polymyositis pathology

• C8+ mediated
• Inflammation around normal muscle fibers
• Scattered necrosis, degeneration, regeneration
• Internal nuclei
• Variability of fiber size but seldom any hypertrophy
• Multifocal: biopsy weak but not wasted

Question 8

Describe treatment of polymyositis

Answer 8

Polymyositis treatment

• Corticosteroids: prednisone or IV solumedrol
• Azathioprine
• Methotrexate
• iVIG
• Rituximab

(take time to be effective)

Question 9

Describe dermatomyositis

Answer 9

Dermatomyositis

• Proximal weakness, dysphagia
• Female more than male
• Children and adults
• Skin manifestations: sun-exposed erythema, heliotrope rash, eczema on extensor surface of joints, hands, knees, elbows
• Other manifestations: ILD (50% anti-Jo-1 positive), malignancy, esophageal disease, vasculopathy in GI tract (kids), myocarditis, calcinosis

Question 10

____ means patient has dermatomyositis

Answer 10

Gottron’s sign means patient has dermatomyositis

(also has extensor surface eczema and rash, heliotrope rash)

Question 11

Dermatomyositis is associated with ____

Answer 11

Dermatomyositis is associated with malignancy

(muscle disease predates oncological manifestations)

Question 12

Describe pathology of dermatomyositis

Answer 12

Dermatomyositis pathology

• Humorally mediated (CD4+): membrane attack complex at normal appearing capillaries
• Perivascular inflammation
• Perifascicular atrophy: may be more apparent on ATPase then H&E stain

(complement deposition towards the edge of muscle -> capillaries infiltrated -> not oxygenated)

Question 13

____ is indicative of dermatomyositis

Answer 13

Perifascicular atrophy is indicative of dermatomyositis

Question 14

Describe treatment for dermatomyositis

Answer 14

Dermatomyositis treatment

• Corticosteroids
• Azathioprine
• Methotrexate
• IVIG
• Rituximab

Question 15

Describe malignancy in dermatomyositis

Answer 15

Dermatomyositis malignancy

• Cancer risk not increased in children
• Need malignancy evaluation and yearly screening for at least 2 years
• Ovarian cancer is most common in dermatomyositis
• Associated malignancy usually detected within 2 years of onset of symptoms but ovarian cancer out to 5 years

Question 16

Describe inclusion body myositis

Answer 16

Inclusion body myositis

• Male predominance
• Most common male inflammatory process over age 50
• Distal weakness
• Asymmetry
• Quadriceps, wrist flexors, finger flexors
• Years for progression

Question 17

Inclusion body myositis is characterized by ____ weakness and ____

Answer 17

Inclusion body myositis is characterized by distal weakness and asymmetry

Question 18

Describe labs in inclusion body myositis

Answer 18

Inclusion body myositis labs

• CK mildly elevated
• NCS may show subclinical sensory neuropathy
• Anti-CNIA antibody: sensitivity of 33%

Question 19

Describe pathology of inclusion body myositis

Answer 19

Inclusion body myositis pathology

• Rimmed vacuoles: seen on H&E but sometimes more apparent on Gomori trichrome
• Vacuoles contain beta-amyloid
• Light microscopy usually good enough for diagnosis

Question 20

____ are indicative of inclusion body myositis

Answer 20

Rimmed vacuoles are indicative of inclusion body myositis

Question 21

____ do not work in treatment of inclusion body myositis while ____ may

Answer 21

Steroids do not work in treatment of inclusion body myositis while IVIG may

Question 22

Describe necrotizing myopathy

Answer 22

Necrotizing myopathy

• Little to no inflammation
• Lots of degeneration
• High CKs
• Relatively acute - 2/3 are from statin use due to antibody against HMG-CoA reductase
• Signal reduction particle
• Paraneoplastic

Question 23

Describe HMG CoA reductase necrotizing myositis

Answer 23

HMG CoA reductase necrotizing myositis (statin associated necrotizing autoimmune myopathy)

• Mostly statin induced
• Antibodies to proteins
• Necrotizing myopathy on biopsy and EMG
• Responds to immunotherapy
• Residual weakness, may relapse with taper of immune modulating medications

Question 24

Describe signal recognition particle myopathy

Answer 24

Signal recognition particle myopathy

• Immune-mediated necrotizing myopathy with myositis-specific autoantibody
• More common in African Americans and women
• CK very high, ANA and ESR often normal
• Necrosis and regeneration is predominant finding on muscle biopsy - minimal to no inflammation
• Dysphagia, Raynaud, myalgias common
• Responds to immunotherapy

Question 25

Summarize the inflammatory myopathies

Answer 25