1q21.1 Recurrent Microdeletion

In: GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993.
[updated ].


Clinical characteristics: The 1q21.1 recurrent microdeletion itself does not appear to lead to a clinically recognizable syndrome as some persons with the deletion have no obvious clinical findings and others have variable findings that most commonly include microcephaly (50%), mild intellectual disability (30%), mildly dysmorphic facial features, and eye abnormalities (26%). Other findings can include cardiac defects, genitourinary anomalies, skeletal malformations, and seizures (~15%). Psychiatric and behavioral abnormalities can include autism spectrum disorders, attention deficit hyperactivity disorder, autistic features, and sleep disturbances.

Diagnosis/testing: The distal 1.35-Mb 1q21.1 recurrent microdeletion can be detected by any number of molecular methods that determine the copy number of sequences within the deleted region, including chromosomal microarray analysis (CMA) using oligonucleotides or polymorphic DNA markers (i.e., SNPs). Fluorescence in situ hybridization (FISH) analysis may be used to test relatives of a proband known to have this deletion.

Management: Treatment of manifestations: Routine treatment of ophthalmologic, cardiac, and neurologic findings; speech, occupational, and physical therapies as appropriate; specialized learning programs to meet individual needs; anti-seizure or antipsychotic medication as needed.

Surveillance: Routine pediatric care; routine developmental assessments; monitoring of specific identified medical issues.

Genetic counseling: The recurrent distal 1.35-Mb 1q21.1 microdeletion is inherited in an autosomal dominant manner. Between 18% and 50% of deletions occur de novo. The microdeletion can be inherited from either parent; a parent with the microdeletion may show a normal phenotype or an abnormal phenotype that is similar to but usually less severe than that of his/her child. Recurrence risk for future pregnancies for parents who do not have the microdeletion is low (probably <1%) but greater than that of the general population because of the possibility of germline mosaicism.

Publication types

  • Review