The Down syndrome patient in dental practice, part I: Pathogenesis and general and dental features

Down syndrome (DS) is an autosomal chromosomal anomaly which results from trisomy of all or part of chromosome 21. It is the single most common genetic cause of mental retardation affecting approximately 1 in 700 live births. Since its first description in 1866 by John Langdon Down, much research has focused on this condition. In the past two decades there has been a significant increase in information about its causes, diagnosis and medical and dental consequences. In this, the first of two articles, we pay tribute to the work of Harvey Brown, and we review the pathogenesis, general and cranio-dental features of Down Syndrome. The cause of DS is usually non-dysjunctive trisomy 21, with 91 percent of cases being maternally derived. Uncommon causes are mosaicism or translocation from other chromosomes. DS patients suffer from congenital cardiopathies, growth retardation, endocrinopathies, sleep apnoea, neoplasias and early-onset Alzheimer's disease. Typically, craniofacial features include midfacial hypoplasia with a resultant flattened face, ocular hypotelorism and mandibular prognathism. The universal characteristic of the DS face is the upward slanting of the palpebral fissures and epicanthic folds. Dental features include tooth size reduction, hypodontia, reduced root lengths, changes in tooth shape and excessive tooth wear.