Myositis

Question 1

What are the clinical manifestations of myositis?

Answer 1

• Slowly progressive, fixed proximal muscle weakness
• ↑ CPK
• post-exertional pain

Question 2

What are Dx criteria for polymoysitis?

Answer 2

• Symmetrical weakness of limb-girdle muscles and anterior neck flexors.
• Biopsy ==> inflammation in center of muscle fascicle, CD8, no B cells, No vasculopathy
• ↑ CPK and serum enzymes (they are variable)
• Electromyographic triad: short, small, polyphasia motor units, fibrillations and sharp waves; and bizarre, repetitive discharges. (Variable)

Question 3

What are clinical manifestations of dermatomyosistis?

Answer 3

• polymyositis + rash
• Lilac HELIOTROPE around eyelids
• Periorbital edema
• Scaly erythema on MCP and PIP (GOTTRON’S SIGN)
• Rash ==> neck and V-SIGN on torso (rash can be elsewhere, too)
• Capillary nail fold changes and PERIIUNUAL ERYTHEMA

Question 4

What are the differences in biopsy features between Polymyositis and Dermatomyositis?

Answer 4

Polymyositis
•	inflammation in center of muscle fascicle
•	CD8, no B cells
•	No vasculopathy
Dermatomyositis
•	inflammation perifascicular muscle
•	CD4, B cells
•	Vasculopathy and complement deposition

Question 5

(detail) What are autoantibodies in polymyositis and dermatomyositis?

Answer 5

• ANA 90% ==> non-specific
• Ro, La, RNP 20% ==> secondary to other autoimmune
• Jo-1 20% ==> PM/DM and myositis specific + LG dz, and raynauds (anti-synthetase syndrome)
• SRP 5% ==> specific to PM ==> prognosis bad
• Mi-2 10% ==> specific to DM

Question 6

What pulmonary dz are associated with myositis?

Answer 6

• interstitial pneumonitis, alveolitis, fiborisis

* LGs are most common secondary organ

Question 7

What are the features of juvenile dermatomyositis?

Answer 7

• Adult +
• Vasculitis
• Lipodystrophy
• Calcinosis

Question 8

What is Tx of PM/DM?

Answer 8

• steroids
• MTX azathioprine
• Skin is difficult to Tx

Question 9

What are the features of Inclusion Body Myositis?

Answer 9

• Rare
• Elderly males
• Weakness pattern&raquo_space; Proximal, symmetric or Distal, Assymmetric
• Intractable to Tx
• Gradual

Question 10

What are the histological features of Inclusion Body Myositis?

Answer 10

• infiltrate, rimmed vacuoles, inclusions, amyloid, mt abnormalities

Question 11

What are examples of myopathies?

Answer 11

Rhabdomyolysis
Drug-induced myopathy (steroids)
Metabolic myopathies
DDx with Polymyalgia Rheumatica and myositis

Question 12

What are differences between statin and steroid myopathies?

Answer 12

Statin Myopathies
•	MYALGIA, WEAKNESS
•	anytime, usually when  Tx is started
•	CPK = 1000
•	Rare aggressive, requires immunosuppression

Steroid Myopathies (sep predinisone)
•	WEAKNESS
•	Type 2 muscle atrophy
•	Prolonged treatments
•	Dx: stop steroids, symptoms improve

Question 13

General Clinical Presentations of Metabolic Myopathies?

Answer 13

•	dynamic weakness
•	exercise intolerance
•	myoglobemia
•	CV and neuro involvements
There are primary and secondary metabolic myopathies. See my notes for details

Question 14

What are the manifestations of Polymyalgia Rheumatica?

Answer 14

• > 50 y/o
• Rapid onset hip/shoulder pain
• Inability to walk due to pain
• Inflammation, but not of muscles ↑ ESR or ↑ CRP
• Tenderness to palpation
• CPK normal, no autoantibodies, strength fine
• Tx steroids with rapid improvement