RHEUM: Dermatomyositis and polymyositis,

Question 2

What is Dermatomyositis and Polymyositis? How would you distinguish them simply?

Answer 2

Autoimmune inflammation of striated muscle. M:F similar peak onset is 40-50 yrs.

Dermatomyositis - muscle weakness and skin rash

Polymyositis - proximal muscle weakness (muscles closest to trunk)

Question 3

Presentation of Dermatomyositis and Polymyositis?

Answer 3

Insidious onset over weeks muscle pain, fatigue and weakness (can be painless)
Bilateral affecting proximal muscles
Shoulder and pelvic girdle affected

Presentation may be accompanied with:
SOB
Rash (Dermatomyositis only)
Raynaud’s common

Question 4

What is the relationship between Dermatomyositis and Polymyositis and malignancy?

Answer 4

Can be caused by underlying malignancy (paraneoplastic syndromes). Risk is greatest in 2-3 yrs before and after diagnosis.

common causes:

Lung
Breast
Ovarian
Gastric

Question 5

Diagnostic criteria for Dermatomyositis and Polymyositis?

Answer 5

Symmetrical muscle weakness
raised serum enzymes e.g. CK, ALT (muscle w/o other LFTS raised)
Electromyographic changes
Biopsy muscle 
Rash of dermatomyositis 

PM if >3 of first 4
DM if >/= 2 of first 3

Autoantibodies :
Anti-Jo- 1 AB - PM
Anti- Mi-2- AB - DM
ANA AB - DM

Question 6

Key investigation result for diagnosing Dermatomyositis and Polymyositis? What other causes of a raised level of this enzyme?

Answer 6

Creatinine Kinase blood test will be high. Inflammation of muscle cells - released.

> 1000 U/L (usually less than 300 U/L)

Other causes:
Rhabdomyolysis
AKI
MI
Statins
Strenuous exercise

Question 7

What are some of the features of Dermatomyositis skin rash?

Answer 7

Photosensitive rash on light exposed places e.g. scalp, neck, back, shoulders, face - lead to post-inflammation hypo/ hyper pigmentation

Gottron lesion - linear erythematous plaques on back of hands

Purple rash on face and eyelids

Periorbital oedema

Subcutaneous calcinosis ( ca deposits in subcut tissue)

‘Mechanics hands’ dry cracked palms and fingers

Question 8

Treatment of Dermatomyositis and Polymyositis?

Answer 8

DRUG 1st Line:
Corticosteroids- main in first weeks

DRUGS Long term / steroids not working:
Immunosuppressants :Methotrexate / Azathioprine
IV immunoglobulins
Biologics: infliximab

Monitoring:
CK levels, EMG studies, MRI, Biopsy

NON DRUG:
Physio / Occupational health - muscle strength / function
Sun protection - HCQ may help with rash
Long term condition - help with this