Table 2.

Bohan and peter criteria for polymyositis and dermatomyositis.

Cretirion	Polymyositis		Dermatomyositis		Details
	Definite	Probable	Definite	Mild or early
Muscle strength	Myopathic muscle weakness	Myopathic muscle weakness	Myopathic muscle weakness	Seemingly normal strength	Symmetrical and progressive weakness of the proximal limb-girdle muscles
Electromyographic findings	Myopathic	Myopathic	Myopathic	Myopathic or nonspecific	Short duration, low amplitude polyphasic units; fibrillations, complex repetitive discharges; positive sharp waves
Muscle enzymes	Elevated (up to 50-fold)	Elevated (up to 50-fold)	Elevated (up to 50-fold)	Elevated (up to 10-fold)	Creatine kinase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, aldolase
Muscle-biology findings	Diagnostic for this type of inflammatory myopathy	Nonspecific myopathy without signs of primary inflammation	Diagnostic	Nonspecific or diagnostic	Perivascular, interfascicular or endomysial inflammatory infiltration; phagocytosis, necrosis, and regeneration of muscle fibers; capillary obliteration and endothelial damage
Rash or calcinosis	Absent	Absent	Present	Present	Heliotrope rash and Gottron’s sign/papules