Testing and diagnosis of CDKL5 disorder

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What tests are used to diagnose CDKL5 disorder?

For infants being seen for the first time, the CDKL5 diagnosis is most often made after a clinical workup for causes of early-life seizures, including genetic testing.

For older children, the diagnosis is likely made in the process of revisiting potential causes for epilepsy and neurodevelopmental disorder, using the same kind of genetic testing.

Evaluation should seek to exclude other causes of early-life seizures, such as structural brain changes on imaging and metabolic disorders. Symptoms of CDKL5 disorder overlap with symptoms of various other neurodevelopmental disorders such as:

  • other genetic early-life epileptic encephalopathies (including channelopathies such as SCN2A or KCNQ2)
  • Rett syndrome (and its early seizure variant)

Genetic tests for CDKL5 variants

Any of the following four methods can establish a diagnosis of CDKL5 disorder:

  • Sequencing of the CDKL5 gene or testing for small deletions or duplications within the gene
  • Testing for a panel of known epilepsy genes
  • Screening with an intellectual disability gene panel
  • Chromosomal microarray to evaluate for larger deletions including the CDKL5 gene
  • Whole exome sequencing

Testing results should be reviewed with an expert in neurogenetics. Sometimes testing reveals variants in the CDKL5 gene that are not already known to be disease associated (called “variants of uncertain significance”). Such cases may require further workup, such as testing of both parents for the variant.  Your doctors will help in determining how likely the variant in the CDKL5 gene is to be responsible for your child’s symptoms.

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