ICD-10-CM > M00-M99 > M60-M63 > M60 > M60.1 > M60.13 M60.13 Interstitial myositis, forearm Non-Billable/Non-Specific Codes M60.131Interstitial myositis, right forearmM60.132Interstitial myositis, left forearmM60.139Interstitial myositis, unspecified forearm