ICD-10-CM > S00-T88 > T20-T25 > T23 > T23.4 > T23.42 T23.42 Corrosion of unspecified degree of single finger (nail) except thumb Non-Billable/Non-Specific Codes T23.421Corrosion of unspecified degree of single right finger (nail) except thumbT23.421A..., initial encounterT23.421D..., subsequent encounterT23.421S..., sequelaT23.422Corrosion of unspecified degree of single left finger (nail) except thumbT23.422A..., initial encounterT23.422D..., subsequent encounterT23.422S..., sequelaT23.429Corrosion of unspecified degree of unspecified single finger (nail) except thumbT23.429A..., initial encounterT23.429D..., subsequent encounterT23.429S..., sequela