Effect of X-Chromosome Aneuploidy on Jaw Growth

Abstract

It is now increasingly evident that chromosomal abnormalities underlie a goodly proportion of congenital abnormalities, between 5 and 15 per cent of children with congenital abnormalities showing evidence of chromosomal deletions or aberrations. Since dentofacial defects are particularly common in developmental abnormalities, and to an extent not in accordance with the concept of stage-specificity, the possible chromosomal basis of dentofacial defects represents a problem in its own right and, when the chromosomal type is known, provides new indications as to the role of chromosomes in controlling developmental timing. This report represents but an initial probe into a subject that holds great promise for future study. It is our sincere hope that this communication will stimulate further inquiry.Loss or duplication of chromosomes other than the exact multiple of the haploid complement is referred to as "aneuploidy." This may involve either the sex chromosomes (X and/or Y) or the autosomes (non-sex chromosomes). Deletion of one of the autosomes in both man and Drosophila appears to be lethal. Several distinct syndromes result from triplication of chromosomes in the 13-15, 18, and 21 groups, but we shall not discuss these here. We shall limit ourselves for the most part to consideration of syndromes that arise because of a gain or loss of X chromosomes. Surprisingly, these symptom complexes are not as rare as one might suppose. In newborns, the XXY or Klinefelter syndrome is present in 0.3 per cent, the XO chromatinnegative Turner syndrome is present in 0.03 per cent, and the XXX syndrome is present in 0.13 per cent.' In individuals institutionalized for mental retardation, the incidence rises to 1.0, 0.05, and 0.4 per cent, respectively.2 These institutions form, then, a ready source of these fascinating patients for study. Since the marked addition of extra X chromosomes (XXXX, XXXXY, and XXYY syndromes) appears to be associated with more severe mental retardation, these individuals are concentrated in this population. However, these syndromes are far less common than the XXY, XO, and XXX symptom complexes. Possibly the most efficient way to screen such a population for purposes of carrying on growth studies is by means of buccal smears for study of Barr bodies. The Barr body represents the tightly coiled or inactive X chromosome, and, since all X chromosomes in excess of one are thought to be "essentially inactive," there is one less Barr body than the number of X chromosomes. For example, individuals with XO (Turner syndrome)

Taurodontism and Klinefelter Syndrome: Case Report and Review of the Literature

“…In the present case, four permanent teeth were absent. As described by some authors 13,18 that the patients with KS have mental retardation as in this patient. Most of the authors described prognatism about the jaws but only a large maxiller arch was seen in this patient.…”

“…2,6, 13 The characteristic clinical findings of this syndrome may vary but most of the patients have infertility, tall, slender body habitus with long legs and shorter torso, a coarse face, skeletal anomalies, hypogonadism, osteoporosis, mental retardation, aspermatogenesis, variable gynecomastia, small testis and penis. In addition to these findings, language delays, learning problems, behavioral difficulties and cardiovascular problems may occur.…”

“…Most of the authors described prognatism about the jaws but only a large maxiller arch was seen in this patient. 2,5,8,10,13,14 The patients with KS are undiagnosed because the clinical findings of the KS are often varied. It was found that nearly three quarters of estimated cases in the general population were undiagnosed.…”

Reduced tooth size in 45,X (Turner syndrome) females

“…Adult stature is typically very short, mean height being about 140 cm, and birth weight also tends to be below average (Hamerton, 1971). Furthermore, craniofacial morphology is altered, with facial retrognathism and flattening of the cranial base (Gorlin et al, 1965;Filipsson et al, 1965). XO individuals also tend to show retardation in skeletal maturation (Tanner et al, 1959;Park et al, 1983).…”

Occlusion in 47,XXY (Klinefelter syndrome) men

“…According to them, Klinefelter patients showed increased mandibular prognathism together with increased maxillary prognathism, which could be related to the altered shape of the cranial base rather than the altered size and position ofthe jaws. Also, Gorlin et al (1965) have suggested that the loss or addition of an X chromosome …”