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Biomedical subjects

D L Viljoen

Publications and source records attributed to D L Viljoen.

At least 19 recordsLinked to original sources
PubMed2003

Eye feature extraction for diagnosing the facial phenotype associated with fetal alcohol syndrome.

Victims of fetal alcohol syndrome (FAS) exhibit a unique facial phenotype that is emphasised in diagnosis. Among the characteristic facial features, several occurring in the region of the orbits can be evaluated quantitatively using distance measurements. An algorithm is described for automatic extraction and measurement of eye features from stereo photographs. The algorithm was applied to photographs of 46 six-seven-year-old children. The approach relies on peak and valley maps and integral projection functions, to locate the eyes and extract the iris, and genetic algorithms to fit cubic splines to the upper and lower eyelids. Measurements obtained automatically using this algorithm were compared with measurements obtained manually from the photographs. Mean absolute differences between automatic and manual measurements were less than 1 mm for palpebral fissure length (PFL) and interpupillary distance (IPD). Absolute differences were less than 1 mm for 80.4% of PFLs and 100% of IPDs. Inner canthal distance and outer canthal distance did not compare favourably with manual measurements.

Algorithms↗
PubMed2001

A spectrum of ABCC6 mutations is responsible for pseudoxanthoma elasticum.

To better understand the pathogenetics of pseudoxanthoma elasticum (PXE), we performed a mutational analysis of ATP-binding cassette subfamily C member 6 (ABCC6) in 122 unrelated patients with PXE, the largest cohort of patients yet studied. Thirty-six mutations were characterized, and, among these, 28 were novel variants (for a total of 43 PXE mutations known to date). Twenty-one alleles were missense variants, six were small insertions or deletions, five were nonsense, two were alleles likely to result in aberrant mRNA splicing, and two were large deletions involving ABCC6. Although most mutations appeared to be unique variants, two disease-causing alleles occurred frequently in apparently unrelated individuals. R1141X was found in our patient cohort at a frequency of 18.8% and was preponderant in European patients. ABCC6del23-29 occurred at a frequency of 12.9% and was prevalent in patients from the United States. These results suggested that R1141X and ABCC6del23-29 might have been derived regionally from founder alleles. Putative disease-causing mutations were identified in approximately 64% of the 244 chromosomes studied, and 85.2% of the 122 patients were found to have at least one disease-causing allele. Our results suggest that a fraction of the undetected mutant alleles could be either genomic rearrangements or mutations occurring in noncoding regions of the ABCC6 gene. The distribution pattern of ABCC6 mutations revealed a cluster of disease-causing variants within exons encoding a large C-terminal cytoplasmic loop and in the C-terminal nucleotide-binding domain (NBD2). We discuss the potential structural and functional significance of this mutation pattern within the context of the complex relationship between the PXE phenotype and the function of ABCC6.

ATP-Binding Cassette Transporters↗
PubMed2001

Fetal alcohol syndrome: an international perspective.

This article represents the proceedings of a workshop at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Kenneth R. Warren and Faye J. Calhoun. The presentations were (1) Epidemiological research on fetal alcohol syndrome (FAS) in the United States, by Philip A. May; (2) An overview of fetal alcohol syndrome in the Western Cape Province of South Africa, by Denis L. Viljoen and Ting-Kai Li; (3) Diagnostic perspectives of fetal alcohol and tobacco syndromes, by Harumi Tanaka; (4) FAS among pupils of special boarding schools and orphanages in Moscow, Russia, by Galina S. Marinicheva and Luther K. Robinson; and (5) Research on FAS and FAE in Germany: Update and perspectives, by Goetz Mundle.

Europe↗
PubMed2001

Alcohol dehydrogenase-2*2 allele is associated with decreased prevalence of fetal alcohol syndrome in the mixed-ancestry population of the Western Cape Province, South Africa.

BACKGROUND: Fetal alcohol syndrome (FAS) is particularly common among the mixed-ancestry population of the Western Cape Province of South Africa and occurs at a frequency of 0.0392-0.0429 (39.2-42.9 of 1000) among 5- to 9-year-old school entrants. While FAS is clearly caused by an environmental insult, studies in twins and mice support a significant genetic contribution to risk for FAS. It is likely that the development of FAS following excessive alcohol exposure is influenced by genetic factors in both the mother and the child. Known polymorphisms of the alcohol dehydrogenase-2 (ADH2) gene resulting in isozymes with different alcohol oxidizing capacities were investigated as possible candidates for influencing the risk for FAS. METHODS: Genotyping was undertaken for the ADH2 locus in 56 FAS-affected children, their 56 mothers, and 178 control individuals of mixed ancestry from the same geographic region. The ADH2 alleles were analyzed for the three groups and the allele frequencies of the mother and FAS-affected children were independently compared with the control group. RESULTS: The ADH2*2 allele was found to be significantly more common in the control group than in the mothers of FAS-affected children (p = 0.025 +/- 0.004) and in the FAS subjects (p = 0.025 +/- 0.004). The ADH2*3 allele frequency was low and was not significantly different between the groups. CONCLUSION: The ADH2*2 allele is significantly more common in control individuals, suggesting that it may either confer protection or be a marker for a protective effect against FAS among individuals of mixed ancestry in the Western Cape Province of South Africa.

Alcohol Dehydrogenase↗
PubMed1999

Proteus syndrome: diagnostic criteria, differential diagnosis, and patient evaluation.

Proteus syndrome is a complex disorder comprising malformations and overgrowth of multiple tissues. The disorder is highly variable and appears to affect patients in a mosaic manner. This intrinsic variability has led to diagnostic confusion associated with a dearth of longitudinal data on the natural history of Proteus syndrome. To clarify some of these issues, a workshop on Proteus syndrome was held in March 1998 at the National Institutes of Health, and participants developed recommendations for diagnostic criteria, differential diagnosis, and guidelines for the evaluation of patients. This is a review of those recommendations.

Diagnosis, Differential↗
PubMed1998

Prader-Willi syndrome in South African patients--clinical and molecular diagnosis.

STUDY OBJECTIVE: To assess clinically South African patients with the putative diagnosis of Prader-Willi syndrome (PWS) and confirm this diagnosis by DNA/molecular analysis. DESIGN: Prospective, nationally based, combined clinical and laboratory study. MAIN RESULTS: Thirty-seven patients with a putative diagnosis of PWS were examined by clinical geneticists. Only 13 (35.1%) of these patients had the diagnosis of PWS confirmed by molecular analysis, and all 13 PWS patients had positive scores using the PWS consensus diagnostic criteria of Holm et al. The clinical features of the remaining 24 (64.9%) non-PWS patients were analysed and 23 did not have the neonatal, infantile and childhood features necessary to warrant consideration of a diagnosis of PWS; neither did they obtain a positive score according to Holm et al.'s criteria. CONCLUSION: PWS was confirmed in only 35% of South African patients with a putative PWS diagnosis, confirming that this condition is overdiagnosed and that the clinical diagnosis is difficult. Clinically, the diagnostic criteria of Holm et al. are of great assistance in making the diagnosis, but it remains essential to confirm the diagnosis by molecular analysis.

Blotting, Southern↗
PubMed1995

Porencephaly and transverse limb defects following severe maternal trauma in early pregnancy.

A 13 year old boy with mental retardation, hemiatrophy and left hemiplegia, right hemifacial microsomia and transverse digital amputations is reported. He is moderately mentally retarded, experiences grand mal seizures and has evidence of a porencephalic cyst in the right frontotemporal region on CT scan. At 52 days post conception his mother was involved in a road traffic accident and suffered extensive bruising of the abdomen and concussion. It is suggested that the patient's congenital anomalies are a consequence of hypoxia and thrombo-embolic events sustained during early pregnancy.

Abnormalities, Multiple↗
PubMed1994

Prevalence of neural tube defects in Cape Town, South Africa.

The aim of the study was to document the frequency of neural tube defects (NTD) over a 20-year period in Cape Town and to determine the effects of race, gender, maternal age, parity and season of conception on the prevalence. Multiple sources of ascertainment were used, including all maternity hospital records, neurosurgical and spinal defects clinic data, as well as those from the Human Genetics Department and Fetal Abnormality Group. The prevalence rates for NTD fluctuated between 1.74 and 0.63 per 1,000 births, but showed no significant trends over the 20-year period. Prevalence rates were highest for the white population group of 2.56 per 1,000 births compared to 0.95 per 1,000 for blacks and 1.05 per 1,000 for those of mixed ancestry. The higher rates in the whites, who are of British and European extraction and belong to the more affluent section of the community, would suggest that the possible effects of nutrition and infection are overshadowed by genetic factors. There was a female preponderance for both spinal bifida (M:F ratio 0.89) and anencephaly (M:F ratio 0.67). The highest NTD rates were found at both ends of the maternal age range (< 20 years and > 35 years of age). The prevalence was highest at the extremes of birth order (1.65 and 1.58 for birth order 1 and > 7, respectively, and 0.56 and 0.45 for birth order 5 and 6, respectively). A seasonal variation occurred which differed from that reported for the Northern Hemisphere and may reflect local climatic conditions.

Adult↗
PubMed1993

Split-foot anomaly, microphthalmia, cleft-lip and cleft-palate, and mental retardation associated with a chromosome 6;13 translocation.

The split-hand/split-foot anomaly is a component of several disorders which may occur sporadically or be transmitted as autosomal dominant or autosomal recessive traits. We describe a severely mentally handicapped patient with ectrodactyly of both feet in association with extreme microphthalmia, central cleft-lip and palate and mental retardation. She has an apparent de novo 46,XX,t(6;13) (q21;q12) unbalanced translocation. Either of these breakpoints may be the locus for the ectrodactyly-ectodermal dysplasia-facial cleft (EEC) syndrome.

Abnormalities, Multiple↗
PubMed1992

Putative monosomy 21 in two patients: clinical findings and investigation using fluorescence in situ hybridization.

Complete monosomy 21 is claimed to be a rare chromosomal disorder in which the cytogenetic investigation is bedevilled by technical difficulties. We describe the disparate clinical features in two patients in whom an initial diagnosis of monosomy 21 was made by routine karyotyping. Fluorescence in situ hybridisation (FISH) confirmed a translocation of chromosome 21 material to the short arm of chromosome 5 and to the X chromosome, respectively. The usefulness of FISH in the investigation of subtle chromosomal rearrangements is hereby demonstrated. These findings also cast doubt on the existence of "pure" monosomy 21 as an entity, and suggest that partial monosomy 21 is a more likely occurrence.

Abnormalities, Multiple↗
PubMed1991

Founder effect in 20 Afrikaner kindreds with pseudoxanthoma elasticum.

The pedigrees of 20 families with pseudoxanthoma elasticum (PXE) were investigated. The analyses involved 13 generations up to and including the initial settlers, who arrived in the Cape before 1660. Four settler surnames predominate in these pedigrees. Because of the marriage patterns of the settlers' descendants it was necessary to classify the four surnames into two groups. It is suggested that these two groups are the founder groups of present-day PXE patients. Similar genealogical studies have been performed on kindreds with familial polyposis, familial heart block and familial hypercholesterolaemia, among other disorders. Due to geographical isolation, political developments and cultural factors in the Afrikaner, these investigations are feasible and often lead to the identification of founder origin.

Female↗
PubMed1991

Prenatal diagnosis in autosomal dominant Beckwith-Wiedemann syndrome.

A 20-year-old woman with Beckwith-Wiedemann syndrome (BWS) was ultrasonographically appraised at intervals during her pregnancy. Unequivocal evidence for a diagnosis of BWS was obtained in the fetus and this was confirmed postnatally. Early ultrasound diagnosis enabled appropriate genetic counselling to be given; neonatal complications, such as hypoglycaemic episodes, were prevented.

Adult↗
PubMed1991

An apparently new mental retardation syndrome in three elderly sisters.

Three elderly sisters with profound mental retardation in association with the clinical features of microcephaly, short stature, brachydactyly type D, flattened occiput, down-slanting palpebral fissures, low-set large ears, broad prominent nose and kyphoscoliosis have been investigated. Each was more than 60 years of age and their clinical features were strikingly similar. The disorder has several manifestations in common with Rubenstein-Taybi syndrome and appears to be inherited as an autosomal recessive in this family.

Abnormalities, Multiple↗
PubMed1991

Deletion of chromosome 13 in Moebius syndrome.

A girl aged 2 1/2 years with Moebius syndrome was found to have a deletion of band q12.2 in chromosome 13 (46,XX,del(13)(q12.2]. This is the second report concerning involvement of chromosome 13q and Moebius syndrome. The observation raises the possibility that a gene responsible for Moebius syndrome is located in this region of chromosome 13.

Child, Preschool↗
PubMed1991

Microcephaly-cardiomyopathy: a new autosomal recessive phenotype?

A distinctive phenotype of severe microcephaly and self-limiting dilated cardiomyopathy has been observed in two sibs suggesting autosomal recessive inheritance. Mental retardation, delayed developmental milestones, and minor dysmorphism were additional features.

Abnormalities, Multiple↗
PubMed1990

Mirror polydactyly: pathogenesis based on a morphogen gradient theory.

We report on an infant with 7 toes of the left foot in a mirror configuration in association with ipsilateral duplication of the calcaneus and fibula, tibial aplasia, femoral hypoplasia, and a teratomatous sacrococcygeal tumour. The possible pathogenetic mechanisms leading to this limb abnormality are discussed with special emphasis on a field morphogen gradient hypothesis.

Female↗
PubMed1990

Plastic surgery in pseudoxanthoma elasticum: experience in nine patients.

Nine women between the ages of 22 and 56 years underwent cosmetic surgery for correction of the severe cutaneous stigmata of pseudoxanthoma elasticum (PXE). The outcome was generally favorable, and follow-up for up to 15 years showed only moderate regression of the skin manifestations. No serious intraoperative or postoperative complications occurred, although tissue friability, poor wound healing, and keloid formation were noted in a minority of persons. An unexpected problem of extrusion of calcium particles through the surgical wound occurred in two individuals. This resulted in delayed healing and unsightly scars.

Adult↗