Table 2.

Diagnostic approach to ICI-related PM/DM.

Any Grade

Neurological and rheumatological anamnesis, rheumatological (inspection of the skin to identify signs suggestive of dermatomyositis) and neurological (muscle strength determination) objective examinations

Blood chemistry tests including: CPK, transaminases (AST, ALT), LDH, aldolase Cardiac enzymes (to identify possible concomitant myocarditis) Markers of inflammation (ESR, CRP) Consider searching for anti-AChR antibodies (to identify possible concomitant MG) and for antibodies causing neurological syndromes and paraneoplastic myositis

Consider a neurophysiological examination (needle EMG, neuromuscular plaque determination to identify possible concomitant MG, or a nerve conduction study to identify possible concomitant neuropathy)

Consider muscle MRI or tissue biopsy if the diagnosis is uncertain

CPK, ESR and CRP for follow-up

Grade 2

In addition to the above: Rapid rheumatological or neurological evaluation

Grade 3

In addition to the above: Urgent rheumatological or neurological evaluation

ICI, immune checkpoint inhibitor; PM/DM, polymyositis/dermatomyositis; CPK, creatine phosphokinase; AST, aspartate aminotransferase; ALT, alanine aminotransferase; LDH, Lactate dehydrogenase; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; AChR, acetylcholine receptor; MG, myasthenia gravis; MRI, magnetic resonance imaging.