Alphabetic Index FY2027

T23.519

Corrosion of first degree of unspecified thumb (nail)

FY2027Chapter 19: Injury, poisoning and certain other consequences of external causes/T20–T25 Burns and corrosions of external body surface, specified by site

Non-billable headerNot valid on its own. Use one of the more specific codes under it.

T23.519 is a non-billable ICD-10-CM code header for corrosion of first degree of unspecified thumb (nail). Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. A 7th character is required to complete the code. Its coding notes include a Code first instruction, a Use additional code instruction and 2 Excludes2 entries.

7th character

Category T23 requires a 7th character.

Assembled code T23.519A Open code

Guidelines tips

From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.

The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.

Guidelines I.C.19.aInjuries: application of 7th charactersRead the official text

Burns are classified by depth, extent and agent. Burns of the same site and side but different degrees take the highest degree. Non-healing burns are coded as acute burns.

Guidelines I.C.19.dBurns: depth, same site, healing and infectionRead the official text

Late effects of burns are coded with 7th character S, and a current burn and a sequela of an old burn can be coded together. An external cause code is used with burns.

Guidelines I.C.19.d.7; I.C.19.d.8; I.C.19.d.9Burn sequelae and external causeRead the official text

Code first

If the underlying condition listed here is present and known, sequence it first.

Inherited from T23.5 Corrosion of first degree of wrist and hand
  • (T51-T65) to identify chemical and intent

Use additional code

Add the listed code as a secondary code, if known.

Inherited from T23.5 Corrosion of first degree of wrist and hand
  • external cause code to identify place (Y92)
Also from chapter/block level (2 notes)
Inherited from T20–T25 Burns and corrosions of external body surface, specified by site
  • code from category T31 or T32 to identify extent of body surface involved
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • code to identify any retained foreign body, if applicable (Z18.-)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (2 notes)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • birth trauma (P10-P15)
  • obstetric trauma (O70-O71)

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (3 notes)
Inherited from T20–T25 Burns and corrosions of external body surface, specified by site
  • burns and corrosions of first degree [erythema]
  • burns and corrosions of second degree [blisters][epidermal loss]
  • burns and corrosions of third degree [deep necrosis of underlying tissue] [full- thickness skin loss]

Notes

Also from chapter/block level (2 notes)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 1 entry

7th-character codes under T23.519 3