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ICD-10-CM 2027 diagnosis code

G40.84KCNQ2-related epilepsy

Not billable — use a more specific code

G40.84 is a header code, so it can't be reported by itself. Choose one of the 4 more specific codes beneath it.

Code last changed in FY2025 (effective October 1, 2024). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G40.84

G40.84 is the ICD-10-CM diagnosis code for KCNQ2-related epilepsy. It belongs to category G40 (epilepsy and recurrent seizures), block G40-G47 (episodic and paroxysmal disorders) and chapter 6 (diseases of the nervous system). It is a header code, so it can't be reported by itself; one of its 4 subcodes must be used instead.

Within G40.8 (other epilepsy and recurrent seizures), G40.84 is specifically for KCNQ2-related epilepsy. Related codes cover other epilepsy (G40.80), Lennox-Gastaut syndrome (G40.81), epileptic spasms (G40.82), Dravet syndrome (G40.83) and other seizures (G40.89).

To report this condition, pick the subcode that matches the documentation: G40.841 (not intractable, with status epilepticus), G40.842 (not intractable, without status epilepticus), G40.843 (intractable, with status epilepticus) and G40.844 (intractable, without status epilepticus).

It was added in FY2025, effective October 1, 2024.

Specific codes under G40.84

Notes that apply from higher levels

Instructions written at a parent level also apply to G40.84.

› From G40 Epilepsy and recurrent seizures
Note
  • the following terms are to be considered equivalent to intractable: pharmacoresistant (pharmacologically resistant), treatment resistant, refractory (medically) and poorly controlled
Excludes1
  • conversion disorder with seizures (F44.5)
  • convulsions NOS (R56.9)
  • post traumatic seizures (R56.1)
  • seizure (convulsive) NOS (R56.9)
  • seizure of newborn (P90)
Excludes2

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2025 (effective 10/1/2024): Added
  • No changes since FY2025.

Common questions about G40.84

Is G40.84 billable?

No. G40.84 is a header code. Report one of its more specific subcodes instead.