craniofacial patterning in klinefelter (47 xxy) adults
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European Journal of Orlhodoitllcs IS 0993) 183-194 1993 European Orthodontic Society
Craniofacial patterning in Klinefelter (47 XXY) adults
T. Brown*, L Alvesalo**, and G. C. Townsend*'Department of Dentistry, The University of Adelaide, South Australia, and "Institute of Dentistry,University of Oulu, Finland
SUMMARY Radiographic cephalometry incorporating a pattern profile analysis was used tocompare 26 adult Klinefelter males from Finland with first degree adult relatives, 15 males and14 females. Compared with female relatives, the 47 XXY males were larger in almost allcraniofacial linear dimensions, but were similar in facial shape apart from greater mandibularprognathism. Mandibular dimensions in particular differed between the Klinefelter and unaffectedmales, the corpus length being larger, the ramus shorter and the gonial angle more obtuse inthe 47 XXY group. The prominent facial profile, most marked in the mandible, was a dominantfeature of the Klinefelter subjects who also displayed a more acute median cranial base anglethan each control group. Generally, Klinefelter morphology was marked by greater variability orpatterning of the craniofacial structures compared with relatives, possibly due to decreaseddevelopmental canalization. It is proposed that the 47 XXY complex may affect endochondralgrowth in the cranial base, as well as having a direct influence on jaw growth.
The syndrome described by Klinefelter et al.(1942) is characterized primarily by hypogonad-ism, gynaecomastia, aspermatogenesis, andsometimes a lowered Leydig cell function.Several male karyotypes with additional Xchromosomes may show similar clinical signsbut true Klinefelter syndrome, with a 47 XXYkaryotype, is confirmed by cytogenetic examina-tion. The syndrome occurs with a frequency ofabout 1 in 500 males and approximately 80 percent of subjects showing the clinical signs havethe 47 XXY karyotype (Klinefelter, 1984;Perwein, 1984). An extensive literature on theclinical, genetic and psychological aspects ofKlinefelter syndrome has accumulated withcomprehensive reviews provided by Bandmannand Breit (1984), and Serensen (1988).
The facial appearance of 47 XXY subjectswas described by Gorlin et al. (1965) who drewattention to the shallow palate and relativemandibular prognathism. A cephalometricstudy of 36 Danish adults with Klinefeltersyndrome was reported by Ingerslev and Krei-borg (1978). In comparisons with 102 normalyoung adult Danish males, the Klinefeltersubjects displayed several distinctive character-istics, namely a smaller calvaria, increasedcranial base flexion, larger gonial angle andmore pronounced maxillary and mandibular
prognathism. When compared graphically withfemale controls, the Klinefelter males weresimilar in calvarial size, but larger in overallsize of the jaws. The authors suggested thatthe increased prognathism of the Klinefeltersubjects might be related to shape of the cranialbase.
Twenty-two adult Klinefelter males werecompared by radiographic cephalometry with28 male and 49 female young adults, all subjectsfrom Belgrade (Babic et al., 1991). On the basisof significant decreases in the size of the anteriorcranial base, face heights and mandibular ramusin Klinefelter subjects compared with normalmales, the authors suggested that the extra Xchromosome reduced craniofacial growth.However, all linear dimensions, apart frommaxillary length, were greater in the Klinefeltergroup than in normal females.
It is noteworthy that further recent resultsclearly indicate that mesial molar occlusion wasa relatively frequent occlusal anomaly in Kline-felter syndrome men (Alvesalo and Laine,1992).
Tooth crown size characteristics of the syn-drome and other sex chromosome aneuploidieswere discussed by Alvesalo (1985) and Town-send et al. (1988). For example, reductions inmesiodistal and buccolingual diameters of per-manent teeth by 6.1 and 2.6 per cent, respect-
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186 T. BROWN ET AL.
ively, were demonstrated in Turner syndrome.In contrast, Klinefelter males showed a 1.8 and1.7 per cent increase in the respective toothdiameters. There appeared to be direct butdifferential effects of X and Y chromosomeson tooth development. Crown size was generallyincreased by additional X or Y chromosomesand reduced by loss of these chromosomes, butthe relative proportions of enamel and dentinediffered depending on the chromosome.
General physical growth is also affected inKlinefelter syndrome. Serensen (1988) foundthat five Klinefelter boys, examined from age3 to 10 years, were approximately 5 cm tallerthan normal male children at each age. Afurther 16 Klinefelter school-boys were signi-ficantly taller than controls from 7 to 15 years.The observed height increase, however, waspredominantly in leg length relative to upperbody segment, a trend that was present beforepuberty. The aberrant growth patterns in chil-dren with abnormalities of the sex chromosomesmight be due to interference with commonmechanisms of growth control according toMiller et al. (1980). This abnormality, theysuggested, might result from a change insensitivity of the growth mechanism or fromprenatal gonadal dysfunction and altered endo-crine control.
As little is known of the craniofacial charac-ters of Klinefelter males from other populations,or the morphological relationships betweenKlinefelter subjects and unaffected members oftheir families, the present study of Finnishindividuals was carried out. The sample of47 XXY subjects was augmented by recordsfrom" a number of first degree relatives parents, brothers and sisters. The analysis islimited to adult members of the study popu-lation.
Subjects and methods
The study was part of a larger investigation ofdental and craniofacial growth and develop-ment, oral health, and anthropometries inFinnish individuals with various sex chromo-some anomalies and their families. Up-to-date313 patients and 371 first-degree relatives havebeen examined. Cytogenetic confirmation ofKlinefelter patients had been made from bloodsamples taken for medical purposes prior to
the dental project. The propositi were ascer-tained through hospitals, cytogenetic units, orthe doctors involved. Hormonal therapy, whenrequired, was usually administered atadulthood.
Standardized lateral head radiographs ofKlinefelter males and their family memberswere examined. However, radiographs wereexcluded if the imaging of important referencepoints was inadequate for their unambiguouslocation, if either jaw was edentulous, or if thedentition was impaired by missing teeth orrestorative procedures to such an extent thatthe position of intercuspal occlusion wasdoubtful.
Radiographs of 40 subjects with Klinefeltersyndrome, who ranged in age from 5 to 58years, were selected for cephalometric analysis.First degree relatives represented by acceptableradiographs totalled 33, comprising 6 fathers,11 brothers, 6 mothers, and 10 sisters. Of the40 Klinefelter subjects, 22 had one relativerepresented, four had two relatives and onehad three relatives; radiographs were either notavailable or unsuitable for any relatives of theremaining 13 Klinefelter subjects.
A subset of 26 lateral head radiographs wasretained for tracing and measurement to repres-ent adult Klinefelter males aged 18-58 yearsand averaging 31 years. Male relatives wererepresented by seven fathers and eight brothers,aged 18-67 years and averaging 37 years. Forthe female relatives, radiographs representingsix mothers and eight sisters, aged 26-51 yearsand averaging 36 years were suitable. Theseadult relatives were accepted for the purposesof the present comparison as the normal Finnishcontrol group.
Pattern Profile Analysis (PPA) as describedby Gam et al. (1984) was the main system forcephalometric analysis. Our implementation ofPPA requires the measurement of 16 key lineardistances representing features of the cranialvault, facial heights and facial depths. Thereference points and variables used in PPA areshown in Figs 1 and 2 and Table 1. A patternprofile is calculated for each subject byexpressing the variables as standard deviatescores, that is z-scores, in relation to a popula-tion standard. For this purpose Gam el al.(1984) used standards calculated from subjectsof the Ann Arbor, Michigan, Growth Study,
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CRANIOFACIAL PATTERN OF KLINEFELTER MALES 187
Figure 1 Cephalometric reference points: 1, gnathion (gn);2, infradentale (id); 3, prosthion (pr); 4, spinal point (sp);5, nasion (n); 6, glabella (gl); 7, sella (s); 8, opisthion (op);9, condylion (cd); 10, condyle-nasion point (cd-n); 11,posterior nasal spine (pns); 12, upper molar cemento-enamel junction (udj); 13, upper alveolar point (uap); 14,lower molar cemento-enamel junction (ldj); 15, mandibularplane point (mp); 16, tangent gonion (tgo); 17, coronoidprocess (cp); 18, incision superius (is); 19, apex superius(as);20, incision inferius (ii); 21, apex inferius (ai); 22, subspinale(ss); 23, supramentale (sm); 24, pogonion (pg); 25, progna-thion (pgn); 26, basion (ba); 27, articulare (ar). Fordefinitions see Gam el al. (1984), and Brown and Travan(1988).
Figure 2 Linear dimensions used in pattern profile analysisand defined in Table 1.
using a larger sample than reported by Rioloet al. (1974). In the present analysis, however,the respective means and standard deviationscomputed for the normal Finnish controls weresubstituted. An index of pattern variability,
calculated as the standard deviation of the 16z-scores, was also derived for each subject. Thisindex, according to Gam et al. (1985), servesas a useful indicator of the extent of craniofacialvariability, the median index for a normalpopulation being around 0.8.
An expanded version of th