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What is CDKL5 Deficiency Disorder?

CDKL5 Deficiency Disorder is a rare x-linked genetic disorder that manifests itself in the first few weeks or months of life with early-onset seizures.   There are estimated to be several thousand cases in the world, but that number changes frequently, as improved genetic testing has evolved and population studies are undertaken.   CDKL5 Disorder is a neurological disorder that causes treatment-resistant seizures and often severe developmental and cognitive impairments.   CDKL5 stands for Cycline-dependent Kinase-like 5.  The CDKL5 gene is located on the short arm of the X chromosome (Xp22.13), and is responsible for making the CDKL5 protein, which is critical for normal brain development and function. Children born with this disorder have impaired CDKL5 protein in the brain.











The CDKL5 gene was first discovered in 2004, and the condition caused by mutations in the CDKL5 gene was originally considered to be a variant of Rett Syndrome.  However, in 2012, a landmark research study argued that CDKL5 is not a variant of Rett Syndrome, but is in fact, a separate and distinct disorder.  This is now widely accepted in the clinical and research community.  However, children with CDKL5 Disorder and Rett Syndrome do share many similar features, which has historically fostered a close relationship between the CDKL5 and Rett Syndrome communities and researchers.  CDKL5 disorder has often been misdiagnosed as Rett Syndrome, Autism, cerebral palsy, and other disorders.

CDKL5 Disorder predominantly affects girls, but 10-20% are boys.  Seizures usually begin in the first 3 to 6 months of life, but on occasion have been diagnosed later in infancy.  Seizures are often difficult to treat, but many achieve seizure freedom for short periods of time, so-called "honeymoon" periods, upon starting a new anti-seizure medication or therapy.   While it is not the norm, it is very important to know that there are many children who have CDKL5 Disorder who never experience seizures, or whose seizures are very well controlled.  

In addition to seizures, the main features of CDKL5 Disorder are developmental delays or impairments in vision (CVI), motor strength, tone, sitting, standing and walking.  Most children experience gastrointestinal problems in varying degrees and severity, and some need assistance with nutritional intake and require a G-tube or other form of tube feeding.  Most children are considered to be non-verbal, with limited communication.  However, it is increasingly clear  that children with this disorder are aware of their surroundings and understand everything that is happening around them, but are unable express what they know.

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