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KANSL1-Related Intellectual Disability Syndrome.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2018.
2010 Jan 26 [updated 2013 Jan 10].

Author information

Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands



The KANSL1-related intellectual disability syndrome is characterized by developmental delay/intellectual disability, neonatal/childhood hypotonia, dysmorphisms, congenital malformations, and behavioral features. Global psychomotor developmental delay is noted in all individuals from an early age. The majority of individuals with the KANSL1-related intellectual disability syndrome function in the mild to moderate range of intellectual disability. Other findings include epilepsy (55%), congenital heart defects (39%), renal and urologic anomalies (37%), and cryptorchidism (71% of males). Behavior in most is described as friendly, amiable, and cooperative.


The syndrome can be caused by a 500- to 650-kb heterozygous deletion at chromosome 17q21.31 that includes KANSL1 or a heterozygous intragenic pathogenic variant in KANSL1. Note: The 17q21.31 microdeletion cannot be identified by routine analysis of G-banded chromosomes or other conventional cytogenetic banding techniques.


Treatment of manifestations: Physiotherapy for feeding problems and motor delay, speech therapy and other interventions to augment communication, educational programs directed to specific disabilities identified. Routine treatment of: epilepsy; scoliosis, hip dislocation, and positional deformities of the feet; cryptorchidism; cardiac, renal, and urologic problems. Surveillance: Routine ophthalmologic examinations for hypermetropia and strabismus; monitoring for progressive spine deformities.


The KANSL1-related intellectual disability syndrome, caused by a microdeletion or a pathogenic variant in KANSL1, is inherited in an autosomal dominant manner, but to date almost all cases result from a de novo deletion or KANSL1 pathogenic variant. Thus, most affected individuals represent simplex cases, i.e., a single occurrence in a family. The recurrence risk for future pregnancies is low (probably <1%) but greater than that of the general population because of the possibility of germline mosaicism in one of the parents. No individuals with KANSL1-related intellectual disability syndrome have been known to reproduce. Prenatal testing is technically feasible, but the likelihood of recurrence in families who have had an affected child is low.

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