X-linked Intellectual Disability

To better serve the growing needs of clinicians and patients, Ambry Genetics offers a range of diagnostic testing options for X-linked Intellectual Disability (XLID). 

 

XLID White Paper

Intellectual disability (ID) is a developmental consequence of both syndromic and nonsyndromic origins. Causes can include complex genetic and hereditary conditions resulting from chromosome or single gene changes, errors during embryogenesis, prenatal and perinatal complications and inborn errors of metabolism.  

DSM-IV-TR* defines ID as follows1:

  • Intelligence quotient (IQ) approximately 70 or below
  • Onset before age 18 years   
  • Impairments in adaptive functioning in at least 2 of the following areas: communication, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health and safety

X-linked intellectual disability (XLID) is associated with more than 200 conditions linked to >90 genes on the X chromosome.2 XLID affects approximately 1/600-1/1000 males and a significant number of females.3  Research shows a direct cause between identified genetic mutations and underlying cause for intellectual disability.  Accompanied findings can also include: congenital anomalies, developmental delay, autistic like and dysmorphic features.

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A tiered approach offers the option of Karyotype, Fragile X DNA analysis with a reflex to mPCR for premutation and full mutation alleles and 180K Oligo Array, as well as SNP plus CGH Array with a reflex to several tests most appropriate to the patient phenotype. 

XLID is a next-generation panel that simultaneously analyzes 81 genes linked to X-linked intellectual disability.  Similarly, First-Tier ExomeTM (~4,000 HGMD-defined genes) and Clinical Diagnostic Exome (~ 20,000 genes in entire NCBI RefSeq) sequencing provides the most comprehensive analysis to date.     

 

1. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision.  Washington, DC, American Psychiatric Association, 2000.  

2. Gecz J et al. Trends in Genetics 2009;25(7):308-3162.

3. Lisik M et al. Med Sci Monit. 2008;14(11):RA221-229