T22.549A (Corrosion of first degree of unspecified axilla, initial encounter) compared with T22.549S (Corrosion of first degree of unspecified axilla, sequela), from the official CMS tabular data. T22.549A and T22.549S code the same injury at a different phase of treatment. MedCoder-derived
Same underlying diagnosis, different encounter phase.
The 7th character records the phase of care for the encounter being coded, so a single encounter takes one of these characters, not several. Review whether both phases belong on the same episode of care.
Source: ICD-10-CM Official Guidelines, Section I.C.19.a
Same injury, other encounter phase. T22.549A and T22.549S code the same injury at a different phase of treatment, set by the 7th character.
The 7th character records the type of care given at the encounter being coded (ICD-10-CM Official Guidelines, Section I.C.19.a), so one encounter takes one of these, not both.
| T22.549ACorrosion of first degree of unspecified axilla, initial encounter | T22.549SCorrosion of first degree of unspecified axilla, sequela | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Corrosion of first degree of unspecified axilla, initial encounter is a billable ICD-10-CM diagnosis code (T22.549A). | Corrosion of first degree of unspecified axilla, sequela is a billable ICD-10-CM diagnosis code (T22.549S). |
| 7th character | The appropriate 7th character is to be added to each code from category T22 | The appropriate 7th character is to be added to each code from category T22 |
| Includes | 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] | 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] |
| Use additional code | external cause code to identify place (Y92) code from category T31 or T32 to identify extent of body surface involved | external cause code to identify place (Y92) code from category T31 or T32 to identify extent of body surface involved |
| Code first | (T51-T65) to identify chemical and intent | (T51-T65) to identify chemical and intent |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources