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Biomedical subjects

D Bixler

Publications and source records attributed to D Bixler.

At least 19 recordsLinked to original sources
PubMed1991

X-linked (recessive) hypomaturation amelogenesis imperfecta: a prosthodontic, genetic, and histopathologic report.

A 16-year-old white girl requested esthetic restorations for her teeth. She was a manifesting heterozygote for the X-linked recessive form of amelogenesis imperfecta with hypomaturation defect. Lyonization theory states that in the somatic cells of female mammals, one of the two X chromosomes is randomly inactivated early in development. Therefore, females who are heterozygous for a given X-linked gene will be mosaic with varying proportions of cells in which only one of a particular pair of alleles is active. This mosaicism produced by lyonization ensures considerable phenotypic variability in the clinical expression of X-linked disorders. Histologic examination of the patient's extracted third molars demonstrated the expected lyonization effect. The patient received six porcelain laminate veneered crowns to restore her maxillary incisor and canine teeth. This article represents the first reported use of such restorations to alleviate the cosmetic and functional handicaps that accompany this genetic disease.

Adolescent↗
PubMed1990

Facial morphometrics in the identification of gene carriers of X-linked hypohidrotic ectodermal dysplasia.

Roentgenographic measurements and morphometric analysis were employed in the investigation of contrasting patterns of craniofacial variation between normal individuals and those affected by X-linked hypohidrotic ectodermal dysplasia (HED). The research objective was to identify and describe the facial characteristics of heterozygous gene carriers who show minor expression of the disorder. In this study of 13 HED families with 16 affected males, 12 carriers, and 12 normal individuals, affected individuals had at least 3 of the following 4 clinical signs and symptoms: a) hypodontia, b) hypohidrosis, c) hypotrichosis, and d) clinically distinct facial physiognomy. By contrast, the gene carriers manifested only one or 2 or none of the 4 clinical manifestations. In a preliminary comparison of gene carriers vs. normal individuals, we have generated 2 discriminant functions (each based on 3 facial measurements taken either from the lateral or frontal cephalograms). These 2 functions correctly diagnose 100% of the gene carriers and normal HED relatives. Facial anomalies characteristic of the gene carriers were 1) abnormally narrow and short maxillary width and palatal depth dimensions; 2) very small and retrusive malar and maxillary regions; 3) markedly reduced lower facial depth, height and width dimensions; 4) small head height, prominent forehead, and high-set orbits; 5) a generalized, symmetric reduction of the whole craniofacial complex.

Adult↗
PubMed1990

Bone dysplasias: the prenatal diagnostic challenge.

The prenatal diagnosis of bone dysplasias presents difficult challenges for the clinician involved in monitoring pregnancies. Such diagnoses highlight delicate ethical issues and may require difficult decision-making when the differential diagnosis includes a lethal bone dysplasia. Despite the rapid technological advances in ultrasonography, the ability to make prenatal diagnoses within this group of disorders is limited by the restricted ultrasonographic capability to appreciate fully the detailed fetal anatomy. However, we perceive that a significant further limitation involves the lack of a systematic protocol to guide the clinician in the ultrasonographic evaluation of a fetus suspected of having a skeletal dysplasia. In an attempt to aid the clinician who is evaluating these suspected pregnancies, we report here 8 cases and propose a model protocol for the ultrasonographic diagnostic approach to fetal skeletal problems in utero.

Adolescent↗
PubMed1990

A morphometric analysis of the fetal craniofacies by ultrasound: fetal cephalometry.

We present here a set of 24 standardized linear measurements that describe the growth of different craniofacial structures in the normal fetus from 16 to 36 weeks of gestation. These measurements were taken from 89 pregnant women, who had from 1 to 3 ultrasonographic evaluations during the pregnancy (16, 26, and 36 weeks of gestation). All the values presented here were obtained using the technique described by Escobar et al. The mean and standard deviation was calculated for each measurement and was used to estimate the normal growth pattern of each variable. Approximate confidence intervals for the mean of each variable were constructed for use in identifying unusually low or high values. The confidence intervals are available in graphic form by request. These data will not only contribute to an understanding of fetal craniofacial growth and development in utero, but in addition, it will help to make the diagnoses of mild craniofacial anomalies that would not be detected by the routine ultrasonographic examination. We suggest that this procedure should be included if not in all routine obstetrical ultrasound evaluations, then at least in the more extensive level II obstetrical ultrasound.

Cephalometry↗
PubMed1990

Improved outcome in Pierre Robin sequence: effect of multidisciplinary evaluation and management.

Infants with complications of Pierre Robin sequence are at increased risk of airway obstruction and resultant hypoxia, cor pulmonale, failure to thrive, and cerebral impairment. In an effort to minimize such complications, patients with Pierre Robin sequence were examined prospectively by a multidisciplinary team using polysomnography and continuous oximetry. Obstructive apnea and desaturation occurred in 18 of the 21 patients studied. Four children required only home apnea monitoring, and six required only monitoring and supplemental oxygen. Seven children had lip-tongue adhesion procedures performed, and four required tracheostomy. No patients died. All patients with isolated Pierre Robin sequence had normal development at follow-up except for one child who had experienced a respiratory arrest before referral. With improvements in neonatal intensive care, testing for respiratory assessment, improved surgical and postoperative intervention and home monitoring, the morbidity and mortality for children with Pierre Robin sequence can be reduced markedly.

Abnormalities, Multiple↗
PubMed1989

Facial dysmorphology, roentgenographic measurements, and clinical genetics.

Roentgenographic measurements are used in the facial diagnosis of a male patient (proband) and his mother with unusual craniofacies. Twenty-four measurements (from both the PA and LA x-ray headplates) defining the major anatomic areas of the head and face were chosen as the overall descriptors for the characterization and recognition of craniofacial pattern profile (CFPP). The measurements were transformed into Z-scores. By using the sigma z (i.e., standard deviation of the z-scores) value, the CFPP deviations were estimated. The proband and mother have aberrant, i.e., dysmorphic, craniofacial pattern profiles. The proband's CFPP is highly stable at two successive ages (6 and 13 years, respectively); only the cranial base and palatal dimensions are becoming increasingly abnormal and asymmetric. Familial as well as syndromic CFPP similarities were assessed. Results of correlation coefficients rz demonstrate a significantly high level of CFPP similarity between the proband and mother. This strongly suggests that the two are the carriers of the same genetic syndrome. Unusual syndrome-specific facial features shared by the two include abnormally large midface, very high-set and widely placed eyes, retrusive and asymmetric upper alveolar region, very small malar bones, and long mastoid processes.

Adolescent↗
PubMed1989

A study of cephalometric features in cleft lip-cleft palate families. I: Phenotypic heterogeneity and genetic predisposition in parents of sporadic cases.

Several previous studies have indicated that unaffected parents of children with nonsyndromic cleft lip and palate show unusual craniofacial features. This study reexamines this question by applying multivariate cluster analysis to lateral cephalometric head plates from 82 individuals who are parents of sporadic cases of cleft lip with or without cleft palate (CL/P). Considerable phenotypic heterogeneity was present within the sample. Three major groupings were defined. Two of these groups showed cephalometric similarities to individuals with overt clefts, while the third showed a generalized concordance to published norms. In almost every case only one member of each parental pair showed the cleft related cephalometric phenotype, suggesting the possibility of a substantial genetic component in many cases of sporadic CL/P. However, there were several cases in which neither parent showed the phenotypic traits. Such cases may have a different etiology or a greater environmental component.

Adult↗
PubMed1979

The human X-chromosome and the levels of serum immunoglobulin M.

The serum concentrations of immunoglobulins G, A and M were measured in a sample of 93 pairs of monozygotic twins, their spouses, and their offspring. The hypothesis that the human X-chromosome carries genes which control the levels of immunoglobulin M was tested with three different approaches. Our results indicate that environmental factors are primarily responsible for the observed variation in the levels of IgG and IgA. The variance of IgM seems to be mostly the result of X-linked gene effects, with women having higher IgM levels than men.

Female↗
PubMed1979

Analysis of intrafamilial correlations, serum levels of IGM and the human X-chromosome.

The serum concentrations of immunoglobulin M (IgM) were measured in a sample of 93 monozygotic twin pairs, their spouses, and their offsprings. The hypothesis that the human X chromosome carries genes that control the levels of IgM was tested with two different approaches neither one of which provided conclusive evidence to support the IgM X-linked gene hypothesis.

Female↗
PubMed1979

Facial clefts in Danish twins.

A total of 74 Danish twin pairs with cleft lip +/- palate (CL(P)) and isolated cleft palate (CP) born in Denmark from 1941 to 1969 were studied. Eight pairs were of indeterminate zygosity status' and 26 pairs of unlike sex were dizygous (DZ). Of the remaining 42 like-sexed pairs, zygosity assignments were made from genotyping and physical resemblance data. Twelve pairs were given MZ status and thirty pairs DZ status. The following data was calculated: 1) in contrast to other reports, the incidence of either CL(P) or CP was not increased for either MZ or DZ twins; 2) using the pairwise method for concordance rate calculation, concordance rates for CL(P) twins were: MZ = 36 per cent; DZ = 1.5 per cent. For CP, MZ = 33 per cent; DZ = 0 per cent. The results support the concept that heredity is a prime factor in the etiology of clefting, but the low MZ concordance rates also suggest genetic heterogeneity in this cleft population.

Cleft Lip↗
PubMed1978

Multiple pterygium syndrome.

After treating a 12-year-old patient with multiple pterygium syndrome, we ascertained the minimal diagnostic criteria of pterygia in the neck, axilla, antecubital, and even popliteal areas; evidence supports autosomal recessive inheritance for this syndrome.

Adult↗
PubMed1978

Linkage studies in Van der Woude syndrome.

A newly ascertained kindred segregating Van der Woude syndrome through four generations is described. Linkage studies using the methods of Ott (1974) were carried out using 19 marker loci.

Amylases↗
PubMed1978

Linkage analysis in dominant acrocephalosyndactyly.

Linkage analysis was performed on a previously reported family in which multiple dominantly inherited acrocephalosyndactyly syndromes were present. An underlying axiom of linkaged analysis is that the trait analysed be monogenic. This prerequisite was presumptively established in the single kindred analysed because acrocephalosyndactyly was observed in multiple cases in multiple generations.

Acrocephalosyndactylia↗