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Molecular Genetics Laboratory

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Atypical Rett Syndrome/X-linked Infantile Spasms (CDKL5 Sequencing and Deletion/Duplication Analysis)

  • LIS Mnemonic: MBCDKL5FS


    Collect whole blood in a purple top (EDTA) tube (preferred). Extracted DNA is accepted.

    Volume Required

    5ml whole blood or 7 ug DNA

    Minimum Required

    3ml whole blood


    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.


    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm


4-6 weeks


81406, 81405

Disease Information

Clinical Features:

X-linked cyclin-dependent kinase-like 5-associated encephalopathy (CDKL5) is an X-linked disorder with a phenotype overlapping that of Rett syndrome and X-linked infantile spasms (ISSX). Rett syndrome is caused by mutations in the MeCP2 gene, and clinical symptoms include loss of speech and purposeful hand use, microcephaly, seizures, ataxia, and stereotypic hand movements. Similar to MECP2, CDKL5 mutations are mostly found in females and rarely in males. The spectrum of phenotypes corresponding to CDKL5-related encephalopathy includes the following: patients with some of the diagnostic criteria of Rett early onset seizure variant, patients characterized by severe encephalopathy with refractory seizures, patients with X-linked infantile spasms and finally, patients with autistic features.

Molecular Genetics:

CDKL5 is located on Xp22 and contains 20 coding exons. CDKL5 is involved in mediating the phosphorylation of the methyl-CpG-binding protein 2 (MECP2). More than 30 pathogenic mutations including missense, nonsense, splice-site and small insertion and deletion mutations have been identified throughout the CDKL5 gene. Germline mosaicism and de novo mutations have been reported.

Detection Rate:

Mutations are present in about 10-17% of the girls affected with early onset seizures or a Rett like phenotype. CDKL5 mutations in males are less common in the literature although studies have shown that CDKL5 mutations are present in boys presenting with severe early-onset encephalopathy and intractable epilepsy.

Related Tests:

Atypical Rett syndrome PANEL/Infantile Spasms PANEL: ARX/MECP2/CDKL5 Sequencing + Deletion/Duplication Analysis Rett syndrome: MECP2 Gene Sequencing Rett syndrome: MECP2 Gene Deletion/Duplication Analysis Infantile Spasms: ARX Sequencing Infantile Spasms: ARX Deletion/Duplication Analysis Congenital Variant of Rett syndrome: FOXG1 Sequencing Congenital Variant of Rett syndrome: FOXG1 Deletion/Duplication Analysis Known mutation analysis is available to family members for mutations previously identified by sequence analysis. Prenatal testing is available to adult females who are confirmed carriers of mutations. Please contact the laboratory director to discuss appropriate testing prior to collecting a prenatal specimen.


Test results with interpretation will be mailed and/or faxed to the referring physician or laboratory following completion of the test. Additional reports will be provided as requested.


The clinical utility of such testing is to support a clinical diagnosis of the disease, facilitate genetic counseling, assess the risk to other first degree relatives and to facilitate testing of at - risk family members.

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