Later studies identified individuals with CASK mutations who had various combinations of milder intellectual disability, microcephaly, congenital nystagmus, and dysmorphic facial features. Some individuals had nonsyndromic intellectual disability. Carrier females were variably affected, with some phenotypically normal.
An Italian family was identified in which a CASK mutation caused a form of FG syndrome (FG syndrome-4). Affected males displayed severe intellectual disability, aggressive and hyperactive behavior, macrocephaly, dysmorphic features, deafness, and severe constipation. Carrier females had mild intellectual disability and mild dysmorphic features.
In a study of 358 probable XLID families, four male probands were found to have CASK mutations. In a study of 45 probands with intellectual disability and either nystagmus or microcephaly, two individuals were found to have CASK mutation; both had nystagmus and intellectual disability.
The CASK gene codes for the calcium/calmodulin-dependent serine protein kinase. The CASK protein interacts with multiple other proteins and is thought to be involved in synaptic interaction, protein trafficking, and regulation of neural development.
For patients with suspected CASK-Related XLID, sequence analysis is recommended as the first step in mutation identification. For patients in whom mutations are not identified by full gene sequencing, deletion/duplication analysis is appropriate.
- OMIM #300749: Mental Retardation and Microcephaly with Pontine and Cerebellar Hypoplasia.
- OMIM #300422: FG Syndrome 4; FGS4.
- Hackett, A. et al. CASK mutations are frequent in males and cause X-linked nystagmus and variable XLMR phenotypes. European Journal of Human Genetics 2010; 18:544-552.
- Hsueh, Y. Calcium/calmodulin-dependent serine protein kinase and mental retardation. Annals of Neurology 2009; 66:438-443.
This test is indicated for:
- Confirmation of a clinical diagnosis of CASK-related XLID in individuals who have tested negative for sequence analysis
- Carrier testing in adult females with a family history of CASK-related XLID in whom sequence analysis was negative.
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Submit copies of diagnostic biochemical test results with the sample, if appropriate. Contact the laboratory if further information is needed.
Sequence analysis is required before deletion/duplication analysis by targeted CGH array. If sequencing is performed outside of EGL Genetics, please submit a copy of the sequencing report with the test requisition.
- Sequencing analysis of the CASK gene is available and is required before deletion/duplication analysis.
- A next-generation sequence analysis panel of 90+ XLID genes is available.
- A CGH array-based test for deletion/duplication analysis of 90+ XLID genes is available.
- Prenataltesting is available to individuals who are confirmed carriers ofmutations. Please contact the laboratory genetic counselor to discussappropriate testing prior to collecting a prenatal specimen.