Myositides

Question 1

Heliotrope rash

Answer 1

Bluish-purple discoloration on the face, eyelids, neck, shoulders, upper chest, elbows, knees, knuckles, and back of patients with dermatomyositis

Question 2

Polymyositis and dermatomyositis comparison

Answer 2

Question 3

Grotton nodules

Answer 3

Flat-topped, raised, nonpruritic lesions found over the dorsum of the MCP, PIP, and DIP in dermatomyositis/polymyositis

Pathology shows acanthosis and papillomatosis

Question 4

Anti-Jo1

Answer 4

Antibody that recognizes cytoplasmic histidyl transferase RNA synthetase

Question 5

Polymyositis

Answer 5

• Onsets in the late teens-early twenties over the course of ~3-6 months
• Often occurs with Sjogren’s syndrome or Rheumatoid arthritis
• Clinical features: Proximal muscle pain and weakness, dysphagia, dyspnea, hoarseness/dysphonia
  
  • Note: Dysphagia is more common with polymyositis than dermatomyositis
• Exam features: Fine pulmonary rales, heart block/bradyarrhythmia, muscle tenderness

Question 6

Dermatomyositis

Answer 6

• Onsets age 40-50 over the course of days to weeks
• Clinical features: Proximal muscle pain and weakness, dysphagia, dyspnea
• Exam features: heliotrope rash, grotton papules, fine pulmonary rales, heart block/bradyarrhythmia, muscle tenderness

Question 7

EKG abnormalities in polymyositis/dermatomyositis

Answer 7

• Left anterior fascicular block
• Right bundle-branch block
• Heart block

Question 8

Historical symptoms of proximal muscle weakness

Answer 8

Upper extremity: Exhaustion with brushing teeth, dropping objects, difficulty reaching overhead

Lower extremity: Difficulty walking up stairs, difficulty rising from a seated position, using arm-rests to aid in standing from a seated position

Question 9

“Shawl sign”

Answer 9

Describes the wrapping of the heliotrope rash around the neck, shoulders, and upper back with relative sparing of the lower chest and lower back

Question 10

Calcinosis cutis

Answer 10

Seen in children with dermatomyositis

Development of dystrophic calcification in the softtissues and muscles, leading to skin ulcers, secondary infection, and joint contractures

Occurs less commonly in adults.

Question 11

Inclusion body myositis

Answer 11

• Presents more commonly in male patients age ~60 years over the course of years
• Often asymmetrical, and also affects distal muscles
  
  • This is a hugely imporant differentiating factor from PM/DM
• Atrophy of the deltoids and quadriceps is often present
• Peripheral neuropathy with loss of DTRs can be present in some patients
• Pathology shows inclusion bodies within muscle and diffuse lymphocytic infiltration (shown)

Question 12

Generally speaking, the definitive diagnosis for any myopathy is ___

Answer 12

Generally speaking, the definitive diagnosis for any myopathy is muscle biopsy

Polymyositis and dermatomyositis you can get away with just demonstrating the presence of specific antibodies, if they are present

Question 13

Diagnosis of inclusion body myositis

Answer 13

• Clinical characteristics
  
  • Asymmetrical proximal and distal muscle weakness (typically involving the deltoids and quadriceps)
• Lab findings:
  
  • Elevated CK (600-800, sometimes normal)
  • Elevated ESR, CRP
  • Autoantibodies:
    
    • anti-Mup44
• Definitive diagnosis: EMC-NCS followed by biopsy

Question 14

Diagnosis of polymyositis/dermatomyositis

Answer 14

• Both are, to some degree, diagnoses of exclusion
• Clinical characteristics
  
  • Proximal muscle weakness
  • Raynaud’s phenomenon
  • Rash
• Lab findings:
  
  • Elevated CK (1,000 - 10,000)
  • Elevated ESR, CRP
  • Associated autoantibodies:
    
    • anti-Jo1
    • anti-PL-7
    • anti-PL-12
    • anti-OJ
    • anti-EJ
• Definitive diagnosis:EMC-NCS followed by biopsy

Question 15

Selecting a muscle to biopsy for suspected myositis syndrome

Answer 15

Should be an atrophied muscle that is likely to demonstrate the pathologic features of end-stage disease

Question 16

Pathologic hallmarks of inclusion body myositis

Answer 16

• Eosinophilic cytoplasmic inclusions
• Vacuoles rimmed with basophilic granules
• Foci that stain Congo red (amyloid)
• On electron microscopy: cytoplasmic helical filaments that contain beta-amyloid

Question 17

Drugs which may induce inflammatory myopathies

Answer 17

• Statins (may be directly metabolic OR may be via anti-HMGCoaR)
• Penicillamine (for Wilson’s disease, soluble copper chelator)
• Ziduvodine (HIV RTI)

Question 18

Polymyositis and dermatomyositis biopsies

Answer 18

Show chronic inflammation and complement deposition

Question 19

Treatment of polymyositis/dermatomyositis/IBM

Answer 19

• Induction: 4-6 weeks of prednisone
• Maintenance: Methotrexate or azathioprine
• Refractory cases: Add IVIg
• Screening: CXR, PFTs, EKG
  
  • If a paramalignant etiology of PM/DM is suspected, CT chet/abd/pelvis is indicated to screen for malignancy. Clinical suspicion for malignancy should remain high for the next few years following diagnosis even if the imaging is negative.
• Rehab: Physical therapy and speech therapy
• Note: IBM is treated effectively the same, but has much worse outcomes. There is little evidence that these treatments even do anything.

Question 20

Most common new-onset myopathy in patients over the age of 50

Answer 20

Inclusion body myositis

Question 21

Most common reason for a misdiagnosis of an inflammatory myopathy

Answer 21

Erroneous pathologic interpretation of the biopsy

A pathology problem!!!

Question 22

Overlap myositis

Answer 22

• Any inflammatory myopathy that occurs in association with features of another autoimmune connective tissue disease.
• A classic form of OM is antisynthetase syndrome:
  
  • Characterized by muscle weakness, Raynaud syndrome, nonerosive arthritis, interstitial lung disease, and skin changes to the palms (mechanic’s hands).
  • Affected patients are positive for antisynthetase antibodies.​

Question 23

Steroid myopathy

Answer 23

Non-inflammatory, corticosteroid-induced muscle wasting

Presents insidiously in proximal muscle groups with lesser effects on distal muscle groups.

Question 24

Immune-mediated necrotizing myopathy

Answer 24

An inflammatory myopathy affecting the proximal skeletal muscles that is particularly severe and associated with a markedly elevated CK level. Progresses over weeks to months.

Associated with anti-SRP antibodies, which is the first-line diagnostic test. A anti-SRP negeative form may evolve out of some cases of dermatomyositis

Treatment is largely the same as for other inflammatory myopathies, but outcomes are worse.

Question 25

Juvenile idiopathic inflammatory myopathy

Answer 25

* Any inflammatory myopathy manifesting in an individual **_\< 18 years old_** * **Juvenile dermatomyositis is most common**, but all others can occur. * **Calcinosis cutis** is very common in juvenile cases. * Often associated with: * **GI disturbances** * **Constitutional symptoms** * **Arthritis**