National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

CDKL5 deficiency disorder


Other Names:
CDKL5; CDKL5 disorder; Early infantile epileptic encephalopathy-2; CDKL5; CDKL5 disorder; Early infantile epileptic encephalopathy-2; X-linked dominant infantile spasm syndrome-2; CDKL5-related disorder; CDKL5 deficiency See More
CDKL5 deficiency disorder is a genetic disorder that causes seizures, developmental delay, and severe intellectual disability. Seizures typically begin within a few months after birth and are difficult to control with medications. Most children have 1 to 5 seizures every day. Other symptoms include problems with sleeping, feeding, and teeth grinding. Gastrointestinal symptoms are also common and may include constipation, reflux, and air swallowing. About 1 in 5 children use a feeding tube. CDKL5 deficiency disorder occurs more often in females than males, and males usually have more severe symptoms. This disorder is caused by a change (pathogenic variant) in the CDKL5 gene that is usually not inherited from either parent (de novo). It is an X-linked dominant disorder. CDKL5 deficiency disorder was once thought to be a variant of Rett syndrome but is now considered a separate disorder.[1][2][3][4]
Last updated: 2/19/2018

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
Learn More:
HPO ID
1%-4% of people have these symptoms
EEG with generalized slow activity 0010845
Percent of people who have these symptoms is not available through HPO
Anteverted nares
Nasal tip, upturned
Upturned nasal tip
Upturned nose
Upturned nostrils
[ more ] 		0000463
Broad forehead
Increased width of the forehead
Wide forehead
[ more ] 		0000337
Cerebral visual impairment 0100704
Constipation 0002019
Deeply set eye
Deep set eye
Deep-set eyes
Sunken eye
[ more ] 		0000490
Developmental regression
Loss of developmental milestones
Mental deterioration in childhood
[ more ] 		0002376
Epileptic encephalopathy 0200134
Gastroesophageal reflux
Acid reflux
Acid reflux disease
Heartburn
[ more ] 		0002020
Generalized hypotonia
Decreased muscle tone
Low muscle tone
[ more ] 		0001290
Generalized myoclonic seizure 0002123
Global developmental delay 0001263
Hyperventilation
Rapid breathing
0002883
Hypsarrhythmia 0002521
Inability to walk 0002540
Infantile onset
Onset in first year of life
Onset in infancy
[ more ] 		0003593
Infantile spasms 0012469
Intellectual disability, profound
IQ less than 20
0002187
Multifocal seizures 0031165
Muscular hypotonia
Low or weak muscle tone
0001252
Myoclonus 0001336
Poor eye contact 0000817
Progressive microcephaly
Progressively abnormally small cranium
Progressively abnormally small skull
[ more ] 		0000253
Prominent forehead
Pronounced forehead
Protruding forehead
[ more ] 		0011220
Scoliosis 0002650
Seizure 0001250
Short foot
Short feet
Small feet
[ more ] 		0001773
Short palm 0004279
Small hand
Disproportionately small hands
0200055
Stereotypy
Repetitive movements
Repetitive or self-injurious behavior
[ more ] 		0000733
Tapered finger
Tapered fingertips
Tapering fingers
[ more ] 		0001182
Thick lower lip vermilion
Increased volume of lower lip
Plump lower lip
Prominent lower lip
[ more ] 		0000179
X-linked dominant inheritance 0001423
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Last updated: 7/1/2020

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

  • The International Foundation for CDKL5 Research has a list of CDKL5 Centers for Excellence. Each clinic provides coordinated care from a team of professionals in different specialties.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to CDKL5 deficiency disorder. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.
  • The Loulou Foundation a private non-profit UK foundation dedicated to advancing research into the understanding and development of therapeutics for CDKL5 deficiency disorder. 
  • The Orphan Disease Center has partnered with the Loulou Foundation to create the CDKL5 Program of Excellence. This program aims to drive the development of effective therapeutic strategies for the treatment of CDKL5 deficiency. The Orphan Disease Center is part of the University of Pennsylvania’s School of Medicine.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The Epilepsy Foundation provides information on CDKL5 deficiency disorder.
  • Genetics Home Reference (GHR) contains information on CDKL5 deficiency disorder. This website is maintained by the National Library of Medicine.
  • The International Foundation for CDKL5 Research has an Introductory Guide on CDKL5 deficiency disorder that includes information on history, diagnosis, symptoms, treatments, therapies, resources, and more.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 

Selected Full-Text Journal Articles

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Bahi-Buisson N, Bienvenu T. CDKL5-Related Disorders: From Clinical Description to Molecular Genetics. Mol Syndromol. April 2012; 2(3-5):137-152.
  2. Mangatt M, Wong K, Anderson B, et al. Prevalence and onset of comorbidities in the CDKL5 disorder differ from Rett syndrome. Orphanet Journal of Rare Diseases. 2016; 11:39. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4832563/.
  3. Fehr S, Wong K, Chin R, et al. Seizure variables and their relationship to genotype and functional abilities in the CDKL5 disorder. Neurology. November 22, 2016; 87(21):2206-2213. https://www.ncbi.nlm.nih.gov/pubmed/27770071.
  4. Fehr S, Wilson M, Downs J, et al. The CDKL5 disorder is an independent clinical entity associated with early-onset encephalopathy. Eur J Hum Genet. March 2013; 21(3):266-73. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3573195/.