ICD-10 Code G40.42 – Cyclin-Dependent Kinase-Like 5 Deficiency Disorder (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G40.42 – Cyclin-Dependent Kinase-Like 5 Deficiency Disorder
What it is
This code identifies cyclin-dependent kinase-like 5 deficiency disorder, a rare genetic epilepsy syndrome. It is used when documentation names CDD or a CDKL5-related developmental and epileptic encephalopathy.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include early-onset seizures, severe developmental delay, and significant neurodevelopmental impairment.
When to use this code
Use G40.42 when the provider documents CDKL5 deficiency disorder, CDKL5-related epilepsy, or a similar confirmed diagnosis. Apply it for encounters focused on this specific epileptic disorder, not for nonspecific seizure symptoms alone. Check documentation if the record is incomplete.
Do not use for
Do not use this code for general epilepsy, febrile seizures, or seizure-like episodes without a documented CDKL5 diagnosis. If the chart only says “seizures,” code the documented condition instead.
Coding tip
Verify that the diagnosis is explicitly tied to CDKL5 before assigning G40.42.