Down syndrome, the most common chromosomal abnormality in man, is caused by trisomy of all or a critical portion of chromosome 21 (21q22.3). The birth prevalence of trisomy 21 syndrome is 1/650 live births, with the risk of having a child with Down syndrome increasing with maternal age (Gorlin et al, 1990). Down syndrome is characterized by a combination of phenotypic features that includes typical dysmorphic features and mental retardation. Congenital malformations of the heart (30-40% of the patients) and gastrointestinal tract are common. Congenital absence of teeth has been reported in 23 to 47% (Gorlin et al, 1990). Lateral maxillary incisors, lower incisors, second premolars, and third molars are the most commonly missing. One or both primary upper lateral incisors are missing in more than 10% of the patients, and peg-shaped maxillary lateral incisors are seen in 10% (Gorlin et al, 1990). Shapira et al (2000) studied hypodontia and other dental anomalies in a sample of 34 individuals with Down syndrome in Israel. In this group, 74% of the individuals lacked one or more third molars, and 60% lacked at least one other tooth. In addition, 25% of the individuals had small or peg-shaped upper lateral incisor(s). With third molars excluded, teeth were missing in 59% of the total sample (Shapira et al, 2000).

Text adapted from Sirpa Arte: Phenotypic and genotypic features of familial hypodontia. Dissertation, Institute of Dentistry, University of Helsinki, Finland, 2001.


Jackson Mouse Genome Database Transgene Database OMIM

Text last edited 09.10.2003 by P.N. , page last created 10.12.2004 by P.N.