ICD-10-CM > S00-T88 > T20-T25 > T23 > T23.4 > T23.41 > T23.419 T23.419 Corrosion of unspecified degree of unspecified thumb (nail) Non-Billable/Non-Specific Codes T23.419A..., initial encounterT23.419D..., subsequent encounterT23.419S..., sequela