FY2027 ICD-10-CM reference

G04.90: Encephalitis and encephalomyelitis, unspecified

By the HCC Buddy Coding Team

The official ICD-10-CM descriptor is Encephalitis and encephalomyelitis, unspecified. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.

Billable code. Verified against the official FY2027 order file.

CMS-HCC V28

No V28 HCC for 2026 dates of service (CMS 2027 Initial ICD-10-CM Mappings)

CMS-HCC V24

Not used for payment year 2027 Medicare Advantage payment

ESRD

No category in the PY2026 CMS mapping; CMS 2027 initial file unchanged

PACE

Source verification pending

RxHCC

No category in the PY2026 CMS mapping; CMS 2027 initial file unchanged

HHS-HCC

HCC 3: Central Nervous System Infections, Except Viral Meningitis

RAF not applicable: HHS-HCC weights vary by metal level. Mapping: HHS-HCC 2026 benefit year.

FY2027 Tabular instructions

Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.

Excludes2

certain conditions originating in the perinatal period (P04-P96)

Source: G00-G99 (chapter, inherited).

Excludes2

certain infectious and parasitic diseases (A00-B99)

Source: G00-G99 (chapter, inherited).

Excludes2

complications of pregnancy, childbirth and the puerperium (O00-O9A)

Source: G00-G99 (chapter, inherited).

Excludes2

congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)

Source: G00-G99 (chapter, inherited).

Excludes2

endocrine, nutritional and metabolic diseases (E00-E88)

Source: G00-G99 (chapter, inherited).

Excludes2

injury, poisoning and certain other consequences of external causes (S00-T88)

Source: G00-G99 (chapter, inherited).

Excludes2

neoplasms (C00-D49)

Source: G00-G99 (chapter, inherited).

Excludes2

symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Source: G00-G99 (chapter, inherited).