Polymyositis and Dermatomyositis

Question 1

what is Polymyositis and dermatomyositis?

Answer 1

autoimmune disorders.

chronic inflammation of muscles (polymyositis)

dermatomyositis is a connective tissue disorder where there is chronic inflammation of skin and muscles

Question 2

investigation for Polymyositis and dermatomyositis

Answer 2

bloods:
- creatinine kinase
(enzyme found in muscle cells) >1000 U/L

(other causes for raised CK are rhabdomyolysis, acute kidney injury, myocardial infarction, statins, strenuous exercise)

Question 3

malignancy and Polymyositis and dermatomyositis

Answer 3

can be caused by an underlying malignancy / paraneoplastic syndromes.

associated with cancers-
lung, breast, ovarian, gastric

Question 4

how does Polymyositis and dermatomyositis present?

Answer 4

Muscle pain, fatigue and weakness
Occurs bilaterally and typically affects the proximal muscles
Mostly affects the shoulder and pelvic girdle
Develops over weeks

• no skin features in polymyositis
• dermatomyositis can involve the skin

Question 5

skin features of dermatomyositis

Answer 5

Gottron lesions (scaly erythematous patches) on the knuckles, elbows and knees. rasied, violaceous and scaly eruptions.

Photosensitive erythematous rash on the back, shoulders and neck

Purple rash on the face and eyelids (heliotrope blue purple discolouration of the upper eyelids)

Periorbital oedema (swelling around the eyes)
Subcutaneous calcinosis (calcium deposits in the subcutaneous tissue)

skin may be scaly, pigmented or depigmented and have shiny appearances.

Question 6

which autoantibodies are involved in Polymyositis and dermatomyositis

Answer 6

Anti-Jo-1 antibodies: polymyositis (but often present in dermatomyositis)
Anti-Mi-2 antibodies: dermatomyositis.
Anti-nuclear antibodies: dermatomyositis.

Question 7

how is polymyositis and dermatomyositis diagnosed?

Answer 7

Clinical presentation

bloods:
Elevated creatine kinase
Autoantibodies

imaging:
Electromyography (EMG)

special:
Muscle biopsy can be used to establish a definitive diagnosis.

Question 8

management of polymyositis and dermatomyositis

Answer 8

rheumatologist
assess for underlying cancer

conservative:
physiotherapy
occupational therapy (muscle strength an function)

medical:
corticosteroids
immunosupressants
IV immunoglobulins
biological therapy (ifliximab)

Question 9

polymyositis increased aldolase

Answer 9

elevated skeletal muscle enzymes- CPK (creation phosphokinase) and alodlase

abnormal EMG results
inflammatory cell infiltrate on uncle bops