International classification of osteochondrodysplasias. International Working Group on Constitutional Diseases of Bone.
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Chromosome Mapping↗
Biomedical subjects
P Beighton
Publications and source records attributed to P Beighton.
Spondyloepiphyseal dysplasia in a Cape Town family: linkage with the gene for type II collagen (COL2A1).
A moderately severe form of autosomal dominant (AD) spondyloepiphyseal dysplasia (SED) has been documented in 14 individuals in 3 generations of a family in Cape Town, South Africa. Affected persons had a short trunk; radiographic investigations indicated that skeletal involvement was worst in the hips and spine. Linkage studies with restriction fragment length polymorphisms (RFLPs) associated with the COL2A1 gene and the phenotype yielded a maximal LOD score of 4.51 at theta = 0.00. This result suggests that the structural locus for type II collagen is primarily involved in the pathogenesis of this form of SED.
Adult↗
Molecular nosology of heritable disorders of connective tissue.
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Collagen↗
Retinitis pigmentosa, AD type I: exclusion of linkage to D3S47 (C17) in a large South African family of British origin.
Linkage analysis has been performed on a large South African family of British origin in which 39 persons in 6 generations had early onset Type I autosomal dominant retinitis pigmentosa (ADRP). Tight linkage was excluded between the disease and the D3S47 locus on chromosome 3. This finding is further evidence for genetic heterogeneity in ADRP.
Chromosomes, Human, Pair 3↗
Adult onset spinocerebellar ataxia linked to HLA in a South African kindred of mixed ancestry.
Hereditary spinocerebellar ataxia (SCA) is a relatively common disorder in the Western Cape region of South Africa. At present there are no genetic markers available for prenatal or presymptomatic diagnosis. A large kindred of mixed ancestry with late onset SCA was studied in which the disorder segregated in an autosomal dominant fashion. HLA typing was undertaken on 44 family members, and the HLA haplotypes were assigned on the basis of segregation. The LIPED computer program, with a correction factor allowing for the age of onset, was used to analyze the pedigree for linkage to HLA. Of 22 individuals in whom disease status could be definitely assessed, only one recombinant between HLA and the SCA locus occurred. The lod score reached a maximum of 4.13 at a recombination fraction of 0.05, indicating the odds to be approximately 13,500 to 1 in favor of linkage between HLA and the putative disease allele for SCA. A possible recombination within the HLA region suggested that the disease allele lies telomeric of the HLA region. In view of the recent demonstration of tight linkage between SCA1 and D6S89, however, HLA should not be used for presymptomatic diagnosis or genetic counselling.
Adolescent↗
Schwartz-Jampel syndrome (chondrodystrophic myotonia).
Schwartz-Jampel syndrome is a rare autosomal recessive disorder. Joint contractures, generalised myotonia, skeletal anomalies, and facial dysmorphism are common features; malignant hyperthermia is a potentially lethal complication during anaesthesia.
Adult↗
Ectodermal dysplasia with blindness in sibs on the island of Rodrigues.
A brother and sister from the island of Rodrigues had mental retardation, blindness owing to severe ocular malformations, short stature, dysmorphic facial features, hypotrichosis, and dental abnormalities. It is likely that they have a hitherto unrecognised autosomal recessive ectodermal dysplasia syndrome.
Adolescent↗
SSCP and segregation analysis of the human type X collagen gene (COL10A1) in heritable forms of chondrodysplasia.
Type X collagen is a homotrimeric, short chain, nonfibrillar collagen that is expressed exclusively by hypertrophic chondrocytes at the sites of endochondral ossification. The distribution and pattern of expression of the type X collagen gene (COL10A1) suggests that mutations altering the structure and synthesis of the protein may be responsible for causing heritable forms of chondrodysplasia. We investigated whether mutations within the human COL10A1 gene were responsible for causing the disorders achondroplasia, hypochondroplasia, pseudoachondroplasia, and thanatophoric dysplasia, by analyzing the coding regions of the gene by using PCR and the single-stranded conformational polymorphism technique. By this approach, seven sequence changes were identified within and flanking the coding regions of the gene of the affected persons. We demonstrated that six of these sequence changes were not responsible for causing these forms of chondrodysplasia but were polymorphic in nature. The sequence changes were used to demonstrate discordant segregation between the COL10A1 locus and achondroplasia and pseudoachondroplasia, in nuclear families. This lack of segregation suggests that mutations within or near the COL10A1 locus are not responsible for these disorders. The seventh sequence change resulted in a valine-to-methionine substitution in the carboxyl-terminal domain of the molecule and was identified in only two hypochondroplasic individuals from a single family. Segregation analysis in this family was inconclusive, and the significance of this substitution remains uncertain.
Base Sequence↗
Waardenburg syndrome (WS) type I is caused by defects at multiple loci, one of which is near ALPP on chromosome 2: first report of the WS consortium.
Previous studies have localized the gene for Waardenburg syndrome (WS) type I to the distal portion of chromosome 2q, near the ALPP locus. We pooled linkage data obtained from 41 WS type I and 3 WS type II families which were typed for six polymorphic loci on chromosome 2q in order to refine the location of the WS locus (WS1) and evaluate the extent of genetic heterogeneity. In the course of this work, we developed diagnostic criteria for genetic and phenotypic studies. Our findings, based on two-locus and multilocus analysis using a linkage map established from reference pedigrees, suggest that there are two or more mutations causing WS, one of which (i.e., WS1) is located on chromosome 2q, between the ALPP and FN1 loci, at distances of 7.8 cM and 11.2 cM for each marker, respectively. The results also indicate that WS1 is responsible for the illness in approximately 45% of all families in this sample. However, the odds favoring this position over a location between ALPP and SAG are only 2:1 when alternate assumptions about the proportion of linked families are considered. We conclude that a more saturated map of this region of chromosome 2q, including highly polymorphic markers, will be needed to accurately distinguish linked families and, ultimately, isolate the mutant gene.
Alkaline Phosphatase↗
Mutations of the KIT (mast/stem cell growth factor receptor) proto-oncogene account for a continuous range of phenotypes in human piebaldism.
Piebaldism is a rare autosomal dominant disorder of pigmentation, characterized by congenital patches of white skin and hair from which melanocytes are absent. We have previously shown that piebaldism can result from missense and frameshift mutations of the KIT proto-oncogene, which encodes the cellular receptor tyrosine kinase for the mast/stem cell growth factor. Here, we report two novel KIT mutations associated with human piebaldism. A proximal frameshift is associated with a mild piebald phenotype, and a splice-junction mutation is associated with a highly variable piebald phenotype. We discuss the apparent relationship between the predicted impact of specific KIT mutations on total KIT-dependent signal transduction and the severity of the resultant piebald phenotypes.
Amino Acid Sequence↗
Phenotypic discriminants in the Waardenburg syndrome.
The gene for Waardenburg syndrome (WS) has been assigned to the locus 2q37 and further molecular investigations of affected families are now urgently required to explore the question of possible genetic heterogeneity. Firm positive or negative diagnosis in family members is crucial for studies of this type, but great variation in phenotypic expression sometimes makes this a difficult matter. Ethnic variation in craniofacial anatomical relationships further complicates the issue. We have attempted to establish diagnostic criteria for WS on the basis of an analysis of the phenotypes in 68 affected children who have been examined in special schools for the deaf in Southern Africa during the past 18 years. We then used these criteria for diagnostic evaluation of all available persons in seven multigeneration WS families in the Cape, as a preliminary to molecular investigations. With very few exceptions this approach permitted firm positive or negative diagnosis in these individuals.
Adolescent↗
Microdeletions in patients with gusher-associated, X-linked mixed deafness (DFN3).
Employing various probes from the proximal part of the Xq21 region, which is known to harbor the DFN3 gene, we have investigated 13 unrelated male probands with X-linked deafness, to detect possible deletions. For two of these patients, microdeletions could be detected by using probe pHU16 (DXS26). One of these deletions also encompasses locus DXS169, indicating that it extends farther toward the centromere. The presence of normal hybridization patterns in the DNA of 25 unrelated control males suggests that these deletions are the primary cause of progressive mixed deafness in these patients. If so, their molecular characterization may pave the way for the identification and isolation of the corresponding gene.
Chromosome Deletion↗
Pseudoxanthoma elasticum: similar autosomal recessive subtype in Belgian and Afrikaner families.
A multidisciplinary survey of the clinical and genetic characteristics of 26 Belgian and 32 Afrikaner families with biopsy-proven pseudoxanthoma elasticum (PXE) was undertaken. The major PXE phenotype emerging from this study is very similar in both patient groups and is characterized by severe ophthalmologic manifestations with variable, mild cutaneous and vascular symptoms. In the families with more than one affected relative, segregation analysis is compatible with autosomal recessive inheritance in both groups. It is suggested that the PXE phenotype of these Belgian and Afrikaner patients is distinct from the other recognized PXE subtypes. The phenotypic resemblance in both patient groups raises the question whether a similar genetic mechanism is involved.
Adult↗
Epiphyseal stippling in acrodysostosis.
Widespread epiphyseal stippling was demonstrated radiologically during the early months of life in 7 children with acrodysostosis. This finding, which does not seem to have been previously documented in this disorder, is important in the differential diagnosis.
Bone Diseases, Developmental↗
The ancestry of spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL) in South Africa.
Comprehensive genealogical investigations have been undertaken in eight families in the Afrikaans-speaking community of South Africa, in which at least one person had spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL). All eight families had ancestral links with two females. These women had multiple marriages and cohabitations during the late 17th and early 18th centuries and they were 12 generations removed from the affected individuals. The identification of these common progenitors confirmed the syndromic homogeneity of SEMDJL in South Africa and permitted recognition of numerous obligate heterozygotes, thus facilitating biomolecular investigations of the basic defect.
Chromosome Mapping↗
Piebaldism: an autonomous autosomal dominant entity.
Piebaldism is a disorder in which the major clinical features are patchy hypopigmentation of the skin and a white forelock. The manifestations of piebaldism overlap with those of other genodermatoses, in particular the Waardenburg syndrome, and it is uncertain whether piebaldism is a distinct entity. We have documented a family in which seven affected members in three generations have gross piebaldism without any additional stigmata. The intrafamilial phenotypic consistency is suggestive that this autosomal dominant disorder has independent syndromic status. Linkage studies using conventional gene markers failed to identity the locus of the faulty gene.
Adolescent↗
Hearing impairment and pigmentary disturbance.
Hearing impairment is a variable manifestation of several heritable conditions in which pigmentation of the skin or eyes is abnormal. Some of these disorders are well recognized although uncommon, while others are virtually private syndromes. Practical issues concerning the major conditions of this type are reviewed in this article on a basis of a survey of 4452 profoundly deaf children attending special schools in Southern Africa, together with investigations in affected families. The Waardenburg syndrome (WS), which is the most common deafness-depigmentation disorder, was present in 121 (2.7%) of the 4452 deaf scholars. Further studies in 7 multigeneration affected families confirmed phenotypic variability and indicated a need for internationally agreed diagnostic criteria. In 4 Cape Town families of mixed ancestry the WS-I gene was linked to the 2q37 locus, but in another large kindred no linkage could be demonstrated. Nonallelic heterogeneity is possible. There is uncertainty concerning possible interrelationship between WS and piebaldism. The phenotypic consistency of a South African family in which 7 persons in 3 generations had gross piebaldism in the absence of disturbance of hearing or involvement of the eyes and periorbital structures is suggestive that this disorder and WS are separate entities. Molecular investigations indicate that the gene for piebaldism in this kindred is not situated at the WS-I locus 2q37. Deafness and hyperpigmentation are present in neurofibromatosis type II (acoustic neuromata) and the multiple lentigines syndrome, while retinal pigmentation is a feature of the Usher syndrome. This latter entity is apparently much less common in Southern Africa than in other parts of the world.
Albinism↗
Profound childhood deafness in southern Africa.
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Africa, Southern↗