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Down syndrome

What are the causes?

Chromosome abnormalities give rise to specific physical features seen in Down syndrome. The range of cognitive disabilities as well as other attributes is enormously wide in Down syndrome. The majority are in the mild range of cognitive ability. Associated defects may include ear and/or eye defects, an increased propensity for infections and heart defects.

A few individuals have the mosaic form of trisomy 21. This means that some body cells have forty-six chromosomes while others have forty-seven. In this form the severity and extent of the condition is dependent upon the proportional relation of normal to abnormal cells.

View Background Background  |  Inheritance patterns and prenatal diagnosis View Inheritance patterns and prenatal diagnosis

Medical text written November 1991 by Contact a Family. Approved November 1991 by Professor M Patton, Professor of Medical Genetics, St Georges Hospital Medical School, London, UK and Dr J E Wraith, Consultant Paediatrician, Royal Manchester Children's Hospital, Manchester, UK. Last reviewed August 2004 by Professor Ben Sacks, Down Syndrome Educational Trust, Portsmouth, UK. Additional genetic information provided June 2005 by Dr L Devlin, Senior Registrar in Genetics, Belfast City Hospital, Belfast, UK.

 

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