Aberrations in Chromosome 1q21.1 Associated With Range of Developmental Disorders in Children

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Title: Aberrations in Chromosome 1q21.1 Associated With Range of Developmental Disorders in Children
URL: http://www.pslgroup.com/dg/22BE8E.htm
Doctor's Guide
September 11, 2008

SEATTLE, Wash -- September 11, 2008 -- Researchers have discovered a submicroscopic aberration in a particular region of human chromosome 1q21.1 that appears to be associated with a variety of developmental disorders in children, according to a study published in the September 11 issue of the New England Journal of Medicine.

According to the authors, the aberration can manifest itself as unexplained mild or moderate mental retardation, growth retardation, learning disabilities, seizures, autism, heart defects, other congenital abnormalities, cataracts, small head size, unusual facial features, hand deformities, or skeletal problems.

Some people who have the aberration are only slightly affected or apparently unaffected, while others are more seriously impaired.

Heather C. Mefford, MD, University of Washington, Seattle, Washington, and Andrew J. Sharp, MD, Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland, and colleagues checked for the presence of microdeletions and microduplications in a specific region of chromosome 1q21.1 in groups of patients with unexplained mental retardation, autism, or congenital abnormalities.

They then compared their findings with similar testing of a group from the general population. In these 4,737 controls from the general population, no microdeletions were found, and only 1 had duplication of the entire region.

The authors explained that the genomic structure of 1q21.1 is extremely complex. There are still 15 assembly gaps, or 700 kb of missing sequence in 1q21.1, in the most recent map of the human genome.

These gaps, the researchers noted, might contain as yet unknown genes that contribute to the differences in the types of developmental abnormalities that occur in children with the deletion.

Supposedly unaffected deletion carriers might in fact have more subtle disorders that could be found during further clinical evaluations. For example, an examination of 1 apparently unaffected carrier revealed mild cataracts and a heart defect that were previously undetected.

Studies by other groups of researchers have also found a connection between 1q21.1 deletions and schizophrenia in some people, and parts missing in the reproductive tract in other people.

The authors recognize that the diversity of disorders and the lack of a distinct syndrome accompanying 1q21.1 rearrangements will complicate genetic diagnosing and counselling.

They suggest that clinicians caring for patients who have unexplained developmental abnormalities consider the identification of a 1q21.1 rearrangement in a patient a significant clinical finding and probably an influential genetic factor contributing to the patient's disorder.

Evaluating the patient's family members may reveal apparently unaffected or mildly affected relatives carrying the same rearrangement. Keeping in mind the many possible repercussions of having this chromosomal rearrangement, the authors suggest that young carriers should be monitored over the long term for the emergence of learning disabilities, autism, schizophrenia, or other neuropsychiatric disorders.

SOURCE: Wake Forest University Baptist Medical Center

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