CDKL5 deficiency disorder

CDKL5 deficiency disorder (CDD) is a developmental and epileptic encephalopathy caused by a pathogenic variant affecting CDKL5. Seizures usually begin in infancy. Development, movement, vision, sleep, gastrointestinal function, breathing, and communication may also be affected. Females are diagnosed more often, but males can also have CDD, and severity overlaps across sexes. The clinical range is broader than early descriptions suggested.1

Urgent safety

Follow the person's seizure action plan. Call emergency services for a seizure that meets the plan's emergency threshold, repeated seizures without recovery, breathing difficulty or color change, serious injury, or a first or substantially changed seizure. Do not give extra rescue medicine outside the prescribed plan.2

Seek urgent assessment for choking, inability to clear secretions, breathing pauses, marked dehydration, or acute loss of alertness or function. A sudden change should not automatically be attributed to CDD.

Clinical pattern and diagnosis

Possible features include:

• early-onset seizures of more than one type, sometimes resistant to treatment;
• developmental differences affecting movement, learning, and communication;
• hypotonia, dystonia, chorea, stereotyped movements, or limited mobility;
• cerebral visual impairment or other visual and eye findings;
• feeding or swallowing difficulty, reflux, constipation, sleep disturbance, and abnormal breathing patterns;
• scoliosis, hip displacement, low bone density, and other musculoskeletal concerns.

Diagnosis requires compatible clinical findings and a pathogenic or likely pathogenic CDKL5 variant. A variant of uncertain significance does not establish the diagnosis. CDD is distinct from Rett syndrome, although older descriptions called it an early-seizure Rett variant. Brain MRI findings may be normal or nonspecific and do not confirm or exclude CDD.1

Most cases result from a new variant, but inheritance and recurrence risk depend on the result and possible parental mosaicism. Genetic counseling should interpret the laboratory report and discuss family testing or reproductive options without assuming one recurrence figure applies to every family.1

Treatment and follow-up

There is no established disease-modifying treatment. Epilepsy care is individualized by seizure type, response, adverse effects, and family priorities. Options may include antiseizure medicines, dietary therapy, or selected procedures. Ganaxolone is FDA approved for seizures associated with CDD in people aged two years and older, but eligibility and monitoring require the treating specialist.2

Care may also involve sleep, respiratory, gastrointestinal, nutrition, vision, orthopedic, rehabilitation, dental, and palliative teams according to need. Medication, diet, standing, seating, mobility, and exercise plans require direct assessment. Avoid attributing pain, reflux, constipation, sleep loss, or medication effects to “behavior.”

Feeding, vision, and communication

Feeding review should consider coughing or choking, respiratory symptoms, prolonged meals, fatigue, weight and hydration, reflux, constipation, positioning, and oral-motor function. Texture, pacing, posture, equipment, tube feeding, and exercises require direct multidisciplinary assessment.1

Speech may be limited or unreliable, but communication ability cannot be inferred from speech or a global developmental score. Observe and respond to gaze, facial expression, body movement, vocalization, gesture, object use, and learned AAC. Offer meaningful choices, allow time, and verify rather than guess.

Use multimodal AAC early and throughout life. Options may include objects, tactile or auditory cues, partner-assisted scanning, signs or gestures, pictures, switches, and speech-generating systems. Cerebral visual impairment can affect visual attention, field preference, contrast, complexity, and fatigue; it does not automatically make eye gaze either suitable or unsuitable. Trial access in familiar activities with vision, motor, seating, seizure, and alertness needs addressed. Train partners, include urgent messages and a reliable yes/no response, and keep a low-tech backup.2 For evaluation, trials, funding, and implementation, use the AAC device acquisition guide.

Coding

• ICD-10-CM G40.42: Cyclin-dependent kinase-like 5 deficiency disorder.

Code associated seizure types, status, and other conditions only when documented and supported by current local coding rules.5

Sources

1. Leonard et al. CDKL5 Deficiency Disorder, GeneReviews — current diagnosis, clinical variability, genetics, surveillance, and management (revised 2025).
2. Amin et al. International consensus recommendations for assessment and management of CDD — multidisciplinary seizure, feeding, vision, development, and communication guidance (2022; PMID 35795799).
3. US Food and Drug Administration: ganaxolone approval for CDD-associated seizures — approved indication and age boundary.
4. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — individualized, multimodal AAC assessment without cognitive prerequisites.
5. Centers for Medicare & Medicaid Services: FY2026 ICD-10-CM definitions — G40.42 descriptor.

Review boundary

This page cannot diagnose CDD, interpret a genetic variant, or remotely assess seizures, breathing, swallowing, nutrition, or pain. Emergencies require immediate local assessment. Rescue medication, other treatment, diet, equipment, mobility, and communication decisions require direct review by qualified clinicians with the person and family.