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T32.99

Billable

Corrosions involving 90% or more of body surface with 90% or more third degree corrosion

Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)

Is T32.99 an HCC code?

Yes. T32.99 maps to Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model (and Severe Skin Burn or Condition under V24).

HCC Category Mapping

V28HCC 385 — Severe Skin Burn or Condition
0.350
V24HCC 162 — Severe Skin Burn or Condition
0.517
ESRDHCC 162 — Severe Skin Burn or Condition
0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for T32.99

For T32.99 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed T32.99 during that encounter — not just copy-forwarded from a problem list.

What This Code Means

T32.99 is the ICD-10-CM diagnosis code for corrosions involving 90% or more of body surface with 90% or more third degree corrosion. Severe chemical burns affecting 90% or more of the body with 90% or more of the burns being the most severe third-degree type, representing near-total full-thickness destruction. T32.99 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering burns and corrosions of multiple and unspecified body regions (t30-t32).

Under the CMS-HCC V28 risk adjustment model, T32.99 maps to Severe Skin Burn or Condition (HCC 385) with a community, non-dual, aged base RAF weight of 0.350. Under the older V24 model, T32.99 mapped to the same category but with a base RAF weight of 0.517 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This is the most severe corrosion classification; document the specific agent causing the corrosion if known. Because T32.99 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for T32.99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •This is the most severe corrosion classification; document the specific agent causing the corrosion if known
  • •Requires seventh character extension and likely multiple additional codes for complications and treatment

Clinical Significance

This represents the most catastrophic chemical burn injury possible, affecting 90% or more of the body with 90% or more being the deepest, most severe third-degree burns. This indicates near-total full-thickness destruction with minimal viable skin remaining and represents the highest severity of chemical injury with extremely grave prognosis and exceptional mortality risk.

Documentation Requirements

  • ✓Total body surface area (90% or greater)
  • ✓Third-degree burn percentage (90% or greater)
  • ✓Chemical agent causing total body destruction
  • ✓Exposure circumstances and timeline
  • ✓Current care status and survival prospects
  • ✓Anatomical assessment of viable tissue
  • ✓Multiple organ system failure
  • ✓Palliative vs. aggressive care decisions

Commonly Confused Codes

  • •T32.98 — Has 80-89% third-degree involvement instead of 90%+
  • •T32.89 — Involves 80-89% total BSA instead of 90%+
  • •T31.99 — Thermal burns rather than chemical corrosions
  • •T32.88 — Different total BSA and third-degree percentages

Code Hierarchy

└T32Corrosions classified according to extent of body surface involved└T32.9Corrosions involving 90% or more of body surface└T32.99Corrosions involving 90% or more of body surface with 90% or more third degree corrosion
└T32.99Corrosions involving 90% or more of body surface with 90% or more third degree corrosion

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