Table 1 Diagnostic criteria of polymyositis and dermatomyositis, according to Bohan and Peter [4, 5].

2. Typical for myositis histopathology findings

3. Elevated plasma level of CK and/or aldolase

4. EMG findings typical for primary myopathy

5. Typical skin findings (Gottron's sign, helitrope rash of eyelids, upper torso, arms)

Diagnosis

Confirmed

Suggestive

Possible

PM

4

3

2

DM

3-4

2

1

plus characteristic skin findings