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

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
1 inclusion term · 5 Excludes1 · 4 Excludes2 · 3 use-additional codes
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 79 · RxHCC V08 category 163

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 023 — CRANIOTOMY WITH MAJOR DEVICE IMPLANT OR ACUTE COMPLEX CNS PRINCIPAL DIAGNOSIS WITH MCC OR ANTINEOPLASTIC IMPLANT OR EPILEPSY WITH NEUROSTIMULATOR (MDC 01)
  • MS-DRG 100 — SEIZURES WITH MCC (MDC 01)
  • MS-DRG 101 — SEIZURES WITHOUT MCC (MDC 01)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 201 — Seizure Disorders and Convulsions

Other models: CMS-HCC V22 HCC 79 · RxHCC V08 HCC 163

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for G40.42 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on G40.42 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • CDKL5

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from G40

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from G40

Use Additional Code

Supplementary codes the tabular list directs you to add.

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

Coder workflow for G40.42

MedCoder structured workflow — derived from this code’s own official record

Before you code G40.42

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with G40.42. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in G40.42’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewF44.5, R56.9, R56.1, P90

Consider G40.42. Then work the Use Additional Code note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Official instructions as workflow

  • Excludes1 — check before selecting G40.42(5 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with G40.42: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareF44.5, R56.9, R56.1, P90

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of G40.42(4 notes)

    Coding workflow: The conditions named in this note are not included in G40.42. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareG93.81, G83.84

    See the official tabular notes · Guidelines I.A.12.b

  • Use Additional Code — after identifying G40.42(3 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with G40.42 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewH47.61, F88

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition G40.42 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewF44.5, R56.9, R56.1, P90

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with G40.42?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

ReviewH47.61, F88

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Cyclin-Dependent Kinase-Like 5 Deficiency Disorder is a billable ICD-10-CM diagnosis code (G40.42).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (2)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. 3 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  2. 5 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
  3. 4 Excludes2 entries — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name G40.42 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 3 Excludes1 notes across 2 chapters: G25.3 — Myoclonus (via G40.-), R56 — Convulsions, not elsewhere classified (via G40.-), R56.1 — Post traumatic seizures (via G40.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 3 Excludes2 notes across 2 chapters: F44.0 — Dissociative amnesia (via G40.-), F44.1 — Dissociative fugue (via G40.-), R25.2 — Cramp and spasm (via G40.4.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 1 Code First instruction: F02 — Dementia in other diseases classified elsewhere (via G40.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Referenced by 2 Use Additional Code instructions: Q87.87 — Hao-Fountain Syndrome (via G40.-), Q93.52 — Phelan-McDermid syndrome (via G40.-).

These codes instruct coders to additionally report this code when it applies.

Referenced by 9 Code Also instructions across 6 chapters: E20.810 — Autosomal dominant hypocalcemia (via G40.-), F78.A1 — SYNGAP1-related intellectual disability (via G40.-), G04.8 — Other encephalitis, myelitis and encephalomyelitis (via G40.-), G43.1 — Migraine with aura (via G40.-), G93.45 — Developmental and epileptic encephalopathy (via G40.-), I67.850 — Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (via G40.-), Q87.85 — MED13L syndrome (via G40.-), QA0 — Neurodevelopmental disorders related to specific genetic pathogenic variants (via G40.-), Z15.1 — Genetic susceptibility to epilepsy and neurodevelopmental disorders (via G40.-).

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 023 (MDC 01), DRG 100 (MDC 01), DRG 101 (MDC 01).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):NVS009 — Epilepsy; convulsions (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Seizure Disorders and Convulsions) for risk-adjusted payment.

G40.211 — Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, with status epilepticus, G40.219 — Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, without status epilepticus, G40.301 — Generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus, G40.309 — Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus, G40.311 — Generalized idiopathic epilepsy and epileptic syndromes, intractable, with status epilepticus, G40.319 — Generalized idiopathic epilepsy and epileptic syndromes, intractable, without status epilepticus, G40.401 — Other generalized epilepsy and epileptic syndromes, not intractable, with status epilepticus, G40.409 — Other generalized epilepsy and epileptic syndromes, not intractable, without status epilepticus, G40.411 — Other generalized epilepsy and epileptic syndromes, intractable, with status epilepticus, G40.419 — Other generalized epilepsy and epileptic syndromes, intractable, without status epilepticus, G40.501 — Epileptic seizures related to external causes, not intractable, with status epilepticus, G40.509 — Epileptic seizures related to external causes, not intractable, without status epilepticus, G40.801 — Other epilepsy, not intractable, with status epilepticus, G40.802 — Other epilepsy, not intractable, without status epilepticus, G40.803 — Other epilepsy, intractable, with status epilepticus, G40.804 — Other epilepsy, intractable, without status epilepticus, G40.811 — Lennox-Gastaut syndrome, not intractable, with status epilepticus, G40.812 — Lennox-Gastaut syndrome, not intractable, without status epilepticus, G40.813 — Lennox-Gastaut syndrome, intractable, with status epilepticus, G40.814 — Lennox-Gastaut syndrome, intractable, without status epilepticus, +43 more

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Epilepsy; convulsions).

G40.211 — Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, with status epilepticus, G40.219 — Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, without status epilepticus, G40.301 — Generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus, G40.309 — Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus, G40.311 — Generalized idiopathic epilepsy and epileptic syndromes, intractable, with status epilepticus, G40.319 — Generalized idiopathic epilepsy and epileptic syndromes, intractable, without status epilepticus, G40.401 — Other generalized epilepsy and epileptic syndromes, not intractable, with status epilepticus, G40.409 — Other generalized epilepsy and epileptic syndromes, not intractable, without status epilepticus, G40.411 — Other generalized epilepsy and epileptic syndromes, intractable, with status epilepticus, G40.419 — Other generalized epilepsy and epileptic syndromes, intractable, without status epilepticus, G40.501 — Epileptic seizures related to external causes, not intractable, with status epilepticus, G40.509 — Epileptic seizures related to external causes, not intractable, without status epilepticus, G40.801 — Other epilepsy, not intractable, with status epilepticus, G40.802 — Other epilepsy, not intractable, without status epilepticus, G40.803 — Other epilepsy, intractable, with status epilepticus, G40.804 — Other epilepsy, intractable, without status epilepticus, G40.811 — Lennox-Gastaut syndrome, not intractable, with status epilepticus, G40.812 — Lennox-Gastaut syndrome, not intractable, without status epilepticus, G40.813 — Lennox-Gastaut syndrome, intractable, with status epilepticus, G40.814 — Lennox-Gastaut syndrome, intractable, without status epilepticus, +42 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Myoclonus, myoclonic, myoclonia”; these codes share that main term but sit in a different category of the Tabular List.

G25.3 — Myoclonus, G51.3 — Clonic hemifacial spasm

Contextual Map

Every relationship of G40.42 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run G40.42 with these 19 related codes in Claim Check

Hierarchy

Use Additional Code

Referenced by Excludes1 notes

Referenced by Excludes2 notes

  • F44.0 — Dissociative amnesia[Excludes2](via G40.-): “postictal amnesia in epilepsy (G40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • F44.1 — Dissociative fugue[Excludes2](via G40.-): “postictal fugue in epilepsy (G40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • R25.2 — Cramp and spasm[Excludes2](via G40.4.-): “infantile spasms (G40.4-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code First instructions

Referenced by Use Additional Code instructions

  • Q87.87 — Hao-Fountain Syndrome[Use Additional Code](via G40.-): “epilepsy, by specific type (G40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • Q93.52 — Phelan-McDermid syndrome[Use Additional Code](via G40.-): “epilepsy and recurrent seizures (G40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code Also instructions (9)

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 201 — Seizure Disorders and Convulsions [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 8,892 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • CDKL5 (Cyclin-Dependent Kinase-Like 5 Deficiency Disorder)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Disorder (of), Cyclin-Dependent Kinase-Like 5 Deficiency (CDKL5)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (40)

Change history

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "G40.42 — Cyclin-Dependent Kinase-Like 5 Deficiency Disorder." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/g40.42-cyclin-dependent-kinase-like-5-deficiency-disorder

Change history

  • FY2021 — October 1, 2020
    Added to the code set
    Cyclin-Dependent Kinase-Like 5 Deficiency Disorder
    FY2021 changes

Nearest Codes in This Family

Official ICD-10-CM classifications closest to G40.42 in its code family, with their registry titles.

View all codes in the G40 family