ICD-10-CM 2027 diagnosis code
G40.42Cyclin-Dependent Kinase-Like 5 Deficiency Disorder
G40.42 is a valid, billable ICD-10-CM code for cyclin-dependent kinase-like 5 deficiency disorder. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for CDKL5.
Code last changed in FY2021 (effective October 1, 2020). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About G40.42
G40.42 is the ICD-10-CM diagnosis code for Cyclin-Dependent Kinase-Like 5 Deficiency Disorder. 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 billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within G40.4 (other generalized epilepsy and epileptic syndromes), G40.42 is specifically for Cyclin-Dependent Kinase-Like 5 Deficiency Disorder. Related codes cover not intractable (G40.40) and intractable (G40.41).
Use an additional code, if known, to identify associated manifestations, such as: cortical blindness (H47.61-) and global developmental delay (F88).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, relative weight 5.7444), DRG 100 (Seizures with MCC, relative weight 1.9233) and DRG 101 (Seizures without MCC, relative weight 0.8952), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It was added in FY2021, effective October 1, 2020.
Coding notes
Notes that apply from higher levels
Instructions written at a parent level also apply to G40.42.
› From G40 Epilepsy and recurrent seizures
- the following terms are to be considered equivalent to intractable: pharmacoresistant (pharmacologically resistant), treatment resistant, refractory (medically) and poorly controlled
Broader instructions also apply from Chapter 6: Diseases of the nervous system.
Alphabetic index entries
2 entriesTerms in the official ICD-10-CM index that lead to G40.42.
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 01 · Diseases and Disorders of the Nervous System
MDC 01 · Diseases and Disorders of the Nervous System
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2021 (effective 10/1/2020): Added
- No changes since FY2021.
Common questions about G40.42
Is G40.42 billable?
- Yes. G40.42 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G40.42 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G40.42 as a principal diagnosis.
Is G40.42 a CC or MCC?
- No. G40.42 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does G40.42 group to?
- G40.42 is used in the MS-DRG v44.0 logic for MS-DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator), MS-DRG 100 (Seizures with MCC) and MS-DRG 101 (Seizures without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.