2026 ICD-10-CM Diagnosis Code G40.42Cyclin-Dependent Kinase-Like 5 Deficiency Disorder

ICD-10-CM Codes›G00–G99›G40-G47›G40

ICD-10-CM G40.42
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G40.42 is a billable ICD-10-CM diagnosis code for Cyclin-Dependent Kinase-Like 5 Deficiency Disorder. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 100 through 101. Coders also document this condition as CDKL5 developmental and epileptic encephalopathy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Epilepsy; convulsions.

Code Identity

ICD-10-CM Code
G40.42
Billable Status
Yes — Valid for Submission
Code Describes
Cyclin-Dependent Kinase-Like 5 Deficiency Disorder
Short Description
Cyclin-Dependent Kinase-Like 5 Deficiency Disorder
Same as the full description in the CMS dataset.
Parent Code
G40.4
Other generalized epilepsy and epileptic syndromes

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG40-G47Episodic and paroxysmal disorders
CategoryG40Epilepsy and recurrent seizures
This CodeG40.42Cyclin-Dependent Kinase-Like 5 Deficiency Disorder

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • CDKL5 developmental and epileptic encephalopathy

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • CDKL5

Use Additional Code

  • code, if known, to identify associated manifestations, such as:
  • cortical blindness H47.61
  • global developmental delay F88

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • CDKL5(Cyclin-Dependent Kinase-Like 5 Deficiency Disorder)
    • Disorder(of)
      • Cyclin-Dependent Kinase-Like 5 Deficiency (CDKL5)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS009
Epilepsy; convulsions
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Epilepsy

Epilepsy is a brain disorder that causes people to have recurring seizures. The seizures happen when clusters of nerve cells, or neurons, in the brain send out the wrong signals. People may have strange sensations and emotions or behave strangely. They may have violent muscle spasms or lose consciousness.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement G40.42 replaces the following previously assigned code(s):

  • G40.89 - Other seizures
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G40.42Overview

Is G40.42 (Other generalized epilepsy and epileptic syndromes) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Cyclin-Dependent Kinase-Like 5 Deficiency Disorder on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does G40.42 group to?

When Cyclin-Dependent Kinase-Like 5 Deficiency Disorder is the principal diagnosis on an inpatient stay, it groups to MS-DRG 100, 101, with relative weights from 0.9026 to 1.9368 depending on complications. Higher weights mean higher Medicare reimbursement.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.