Traits

Traits linked to CDKL5

cyclin dependent kinase like 5

The Human Phenotype Ontology links 146 traits to CDKL5, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
EEG with generalized slow activity	Always
Epilepsy	Always
Global developmental delay	Always
Abnormal gait	Very often (80–99%)
Abnormality of movement	Very often (80–99%)
Agitation	Very often (80–99%)
Autism spectrum disorder	Very often (80–99%)
Difficulty sleeping	Very often (80–99%)
EEG abnormality	Very often (80–99%)
Epileptic encephalopathy	Very often (80–99%)
Focal motor seizure	Very often (80–99%)
Generalized myoclonic seizure	Very often (80–99%)
Generalized tonic seizure	Very often (80–99%)
Hypsarrhythmia	Very often (80–99%)
Infantile spasms	Very often (80–99%)
Intellectual disability	Very often (80–99%)
Involuntary movements	Very often (80–99%)
Jerking	Very often (80–99%)
Loss of developmental milestones	Very often (80–99%)
Loss of speech	Very often (80–99%)
Poor eye contact	Very often (80–99%)
Stereotypical hand wringing	Very often (80–99%)
Abnormality of the nervous system	Often (30–79%)
Apraxia	Often (30–79%)
Delayed motor skills	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Dystonia	Often (30–79%)
EEG with burst suppression	Often (30–79%)
Focal tonic seizure	Often (30–79%)
Generalized-onset seizure	Often (30–79%)
Grand mal seizures	Often (30–79%)
Hand apraxia	Often (30–79%)
Impaired pain sensation	Often (30–79%)
Inability to coordinate movements when walking	Often (30–79%)
Inability to speak	Often (30–79%)
Inability to walk	Often (30–79%)
Increased reflexes	Often (30–79%)
Lethargy	Often (30–79%)
Limb myoclonus	Often (30–79%)
Loss of ability to walk	Often (30–79%)
Moderate global developmental delay	Often (30–79%)
Multifocal epileptiform discharges	Often (30–79%)
Myoclonic seizure	Often (30–79%)
Neonatal seizure	Often (30–79%)
Poor social interactions	Often (30–79%)
Repetitive movements	Often (30–79%)
Restrictive behavior	Often (30–79%)
Seizure affecting one half of brain	Often (30–79%)
Severe global developmental delay	Often (30–79%)
Sleep-wake cycle disturbance	Often (30–79%)
Tactile hypersensitivity	Often (30–79%)
Teeth grinding	Often (30–79%)
Tongue thrusting	Often (30–79%)
Brief seizures with staring spells	Sometimes (5–29%)
Chorea	Sometimes (5–29%)
Choreoathetosis	Sometimes (5–29%)
Degeneration of cerebellum	Sometimes (5–29%)
Delayed myelination	Sometimes (5–29%)
Developmental stagnation	Sometimes (5–29%)
Diffuse cerebral atrophy	Sometimes (5–29%)
Diffuse white matter abnormalities	Sometimes (5–29%)
Disorder of involuntary muscle movements	Sometimes (5–29%)
EEG with spike-wave complexes	Sometimes (5–29%)
Episodic ataxia	Sometimes (5–29%)
Febrile seizure (within the age range of 3 months to 6 years)	Sometimes (5–29%)
Fewer and broader ridges in brain	Sometimes (5–29%)
Generalized clonic seizure	Sometimes (5–29%)
Inappropriate crying	Sometimes (5–29%)
Inappropriate laughter	Sometimes (5–29%)
Intellectual disability, mild	Sometimes (5–29%)
More active than typical	Sometimes (5–29%)
Panic attack	Sometimes (5–29%)
Paroxysmal bursts of laughter	Sometimes (5–29%)
Pill-rolling tremor	Sometimes (5–29%)
Self-injurious behavior	Sometimes (5–29%)
Sudden loss of muscle tone	Sometimes (5–29%)
Tremor	Sometimes (5–29%)
Underdevelopment of part of brain called corpus callosum	Sometimes (5–29%)
Uni- and bilateral multifocal epileptiform discharges	Sometimes (5–29%)
IQ less than 20	Not recorded
Multifocal seizures	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Broad forehead	Often (30–79%)
Deep philtrum	Often (30–79%)
Development of small head that was not present at birth	Often (30–79%)
Drooping lower lip	Often (30–79%)
Full lips	Often (30–79%)
Prominent forehead	Often (30–79%)
Abnormally small head	Sometimes (5–29%)
High forehead	Sometimes (5–29%)
Monobrow	Sometimes (5–29%)
Narrow forehead	Sometimes (5–29%)
Cleft palate	Rarely (1–4%)
Depressed nasal bridge	Rarely (1–4%)
Nasal tip, upturned	Rarely (1–4%)
Sloping forehead	Rarely (1–4%)
Full lower lip	Not recorded
Progressively abnormally small cranium	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Functional motor deficit	Very often (80–99%)
Scoliosis	Very often (80–99%)
Abnormal muscle tone	Often (30–79%)
Decreased muscle tone in infant	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Often (30–79%)
Low muscle tone	Often (30–79%)
Poor head control	Often (30–79%)
Hunched back	Sometimes (5–29%)
Low muscle tone, in neonatal onset	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Broad innermost finger bones of the hand	Often (30–79%)
Short foot	Often (30–79%)
Small hand	Often (30–79%)
Bunion	Sometimes (5–29%)
Broad finger	Rarely (1–4%)
Short finger	Rarely (1–4%)
Wide toe bones	Rarely (1–4%)
Tapered finger	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties	Very often (80–99%)
Acid reflux	Often (30–79%)
Constipation	Often (30–79%)
Functional abnormality of the gastrointestinal tract	Often (30–79%)
Gastrostomy tube feeding in infancy	Often (30–79%)
Poor suck	Often (30–79%)
Poor swallowing	Often (30–79%)
Umbilical hernia	Rarely (1–4%)

Abnormality of the eye

Trait	How often it is seen
Cerebral visual impairment	Often (30–79%)
Deeply set eye	Often (30–79%)
Inward turning cross eyed	Sometimes (5–29%)
Outward facing eye ball	Sometimes (5–29%)
Cross-eyed	Rarely (1–4%)
Total ophthalmoplegia	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Abnormal pattern of respiration	Very often (80–99%)
Episodic tachypnea	Often (30–79%)
Sudden episodic apnea	Often (30–79%)
Apnea	Sometimes (5–29%)
Rapid breathing	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Renal dysplasia	Rarely (1–4%)
Short penis	Rarely (1–4%)
Ureterocele	Rarely (1–4%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent respiratory infections	Often (30–79%)
Recurrent chest infections	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Abnormal skin structure	Often (30–79%)
Absent thumbnail	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Growth delay	Often (30–79%)
Faltering weight	Rarely (1–4%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Hole in heart wall separating two lower heart chambers	Rarely (1–4%)

Abnormality of the endocrine system

Trait	How often it is seen
Early onset of puberty	Rarely (1–4%)

Constitutional symptom

Trait	How often it is seen
Coldness	Often (30–79%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to CDKL5 and how often each is seen. Find out more at hpo.jax.org.

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