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Down syndrome: Clinical features and diagnosis

Kathryn K Ostermaier, MD, FAAP
Section Editors
Jan E Drutz, MD
Helen V Firth, DM, FRCP, DCH
Deputy Editor
Elizabeth TePas, MD, MS


Down syndrome (DS) is the most common chromosome abnormality among liveborn infants. It is the most frequent form of intellectual disability (mental retardation) caused by a microscopically demonstrable chromosomal aberration. DS is characterized by a variety of dysmorphic features, congenital malformations, and other health problems and medical conditions. Not all of them are present in each affected individual. The impact of DS for each person is individual, with some individuals being profoundly impacted while others are healthy and able to live independently as adults. In general, individuals with DS are now reaching fuller potentials secondary to better educational programs, medical advancements, community resources, and the support of family and friends.

The clinical features and diagnosis of DS will be presented here. The epidemiology, genetics, and management are discussed separately. (See "Down syndrome: Overview of prenatal screening" and "Congenital cytogenetic abnormalities", section on 'Trisomy 21 (Down syndrome)' and "Down syndrome: Management".)


Upslanting palpebral fissures, epicanthic folds, and brachycephaly are nearly universal features of DS. The other characteristic dysmorphic features of DS are each present in 47 to 82 percent of cases [1,2]. These features predominantly affect the head and neck and the extremities.

Head and neck — Characteristic dysmorphic features of DS affecting the head and neck include:

Upslanting palpebral fissures

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Literature review current through: Nov 2017. | This topic last updated: Jul 28, 2017.
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