Trisomy 21

This project investigates different aspects of craniofacial phenotypes exhibited in individuals with Down syndrome (DS), siblings of individuals with DS, and typically developing sibling pairs. A human sample (4-12 yrs.) consisting of 3D facial surface images (n = 55 for four separate samples: i.e. n = 220 overall) was used to explore developmental instability of the face and patterns of facial covariation between individuals with DS, their siblings, and typically developing sibling pairs. Morphometric analyses were used to infer how gene-dosage imbalance, caused by trisomy 21, is affecting DS craniofacial development. Overall we found increased fluctuating asymmetry in the faces of individuals with DS, which provides evidence for the "amplified developmental instability" model put forth by Shapiro (1975, 1983). However, the patterns of differences that we found suggest specific disruptions to regions of the face during craniofacial development rather than the generalized disruptions described by Shapiro under the amplified developmental instability model. Additionally, the results of our investigation found that covariation of facial metrics is different in DS individuals and in DS siblings relative to typically developing siblings. Based on differences in the pattern and strength of integration within and between facial regions in the DS and DS sibling samples, we put forth an "aneuploid conception model" to explain why facial integration is lowest in DS siblings and strengthened in DS relative to DS siblings.

In addition to the human-based analyses, micro-computed tomography (µCT) scans and morphometric analysis were employed to evaluate a complete genetic mouse model for DS - the Ts1Yey mouse. Morphometric comparison of craniofacial measures for Ts1Yey mice and euploid littermates (n = 12 for each sample) was done to determine if this model exhibits craniofacial differences similar to differences seen in humans with DS and in previously established DS mouse models. Overall, our results validate this mouse model for use in craniofacial DS investigations.

Periodontal disease is highly prevalent in Down syndrome (DS) individuals and is a significant cause of tooth loss in these individuals. Alterations in the immune system associated with poor oral hygiene, normally observed in these patients, are important contributing factors for the increased susceptibility to periodontal disease. The etiology of periodontal disease in DS is complex and more recently much focus has been placed in understanding the immune response alterations resulting from this genetic disorder. The purpose of this paper is to review the literature on the immunological alterations observed in Down syndrome patients and their relationship to periodontal disease. The increased incidence of periodontal disease in DS subjects relates to its genetic background. The reduced ability of the immune system to properly eliminate periodontal pathogens may be the main reason behind the increased susceptibility to periodontitis. Evaluation, treatment and monitoring of these patients as early as during the primary dentition can reduce the morbidity associated with periodontal disease.

Down syndrome was first medically described as a separate condition from other forms of cognitive impairment in 1866. Because it took so long for Down syndrome to be recognized as a clinical entity deserving its own status, several investigators have questioned whether or not Down syndrome was ever recognized before 1866. Few cases of ancient skeletal remains have been documented to have Down syndrome-like characteristics. However, several forms of material culture may depict this condition. Within this paper the history of our understanding of Down syndrome is discussed. Both skeletal remains and different forms of material culture that may depict Down syndrome are described, and where relevant, debates within the literature about how likely such qualitative diagnoses are to be correct are also discussed. Suggestions are then made for ways in which a quantitative diagnosis can be made to either strengthen or weaken qualitative arguments for or against the diagnosis of Down syndrome in different forms of historic material culture.

Recommended Citation
Starbuck, John M. (2011) "On the Antiquity of Trisomy 21: Moving Towards a Quantitative Diagnosis of Down Syndrome in Historic Material Culture," Journal of Contemporary Anthropology: Vol. 2: Iss. 1, Article 2.
Available at: http://docs.lib.purdue.edu/jca/vol2/iss1/2

Clinical and cytogenetic data of two related patients, both trisomic for the segment 4q27→qter, are reported. Familial studies determined that the mothers of the two probands were carriers of the same balanced translocation between chromosomes 4 and 18. Altogether, two partial trisomies 4q, five balanced karyotypes, and one 45,XO karyotype were found in the family. The 18 cases reported to date are reviewed with respect ot the karyotype-phenotype correlation.