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PubMed2003

Is the novel SCKL3 at 14q23 the predominant Seckel locus?

Seckel syndrome (SCKL) is a rare disease with wide phenotypic heterogeneity. A locus (SCKL1) has been identified at 3q and another (SCKL2) at 18p, both in single kindreds afflicted with the syndrome. We report here a novel locus (SCKL3) at 14q by linkage analysis in 13 Turkish families. In total, 18 affected and 10 unaffected sibs were included in the study. Of the 10 informative families, nine with parental consanguinity and one reportedly nonconsanguineous but with two affected sibs, five were indicative of linkage to the novel locus. One of those families also linked to the SCKL1 locus. A consanguineous family with one affected sib was indicative of linkage to SCKL2. The novel gene locus SCKL3 is 1.18 cM and harbors ménage a trois 1, a gene with a role in DNA repair.

Abnormalities, Multiple↗

PubMed2003

Molecular basis of lipoid proteinosis in a Libyan family.

Lipoid proteinosis is an autosomal recessive condition associated with variable scarring and infiltration of skin and mucosae. The disorder has recently been shown to result from loss-of-function mutations in the extracellular matrix protein 1 gene (ECM1) on 1q21. Extracellular matrix protein 1 has important physiological and biological roles in aspects of epidermal differentiation, binding of dermal collagens and proteoglycans, and in regulation of angiogenesis. Thus far pathogenic mutations have been described in 16 different families with lipoid proteinosis throughout the world. In this report, we describe the clinico-pathological features of a 10-year-old boy with lipoid proteinosis from a consanguineous Libyan family. By direct sequencing of the affected individual's genomic DNA, we identified a homozygous nonsense mutation in exon 2 of the ECM1 gene, Q32X. This mutation is the most 5' of all ECM1 mutations described thus far and is predicted to ablate the ECM1a, ECM1b and ECM1c splice variants of the ECM1 gene and to result in a severe clinical phenotype. Sequencing of DNA from the affected individual's five siblings revealed that four were heterozygous carriers of Q32X, findings that have important implications for genetic counselling given the high frequency of consanguineous marriages in Libya.

Child↗

PubMed2000

In-utero diagnosis of mucopolysaccharidosis type VII in a fetus with an enlarged nuchal translucency.

Mucopolysaccharidosis type VII was diagnosed prenatally during the first pregnancy of a Turkish consanguineous couple, following diagnostic work-up of an increased nuchal translucency detected by ultrasound at 13 weeks of gestation. Mucopolysaccharidosis type VII (MPS VII) or Sly syndrome is a rare autosomal recessive lysosomal storage disease, caused by the deficiency of the enzyme beta-glucuronidase. The most severe form of MPS VII manifests itself by non-immune fetal hydrops. Tests for the diagnosis of metabolic disorders, especially lysosomal diseases, are essential when the major causes of hydrops fetalis have been excluded. The presence of a beta-glucosidase deficiency, Gaucher's disease, in the infant of the patient's sister emphasizes the importance of a complete family history in consanguineous couples and the risk for several recessive diseases in some families.

Adult↗

PubMed1995

Determinants of term intrauterine growth retardation: the Saudi experience.

In a clinical study from an unselected Saudi obstetric population, the incidence of and risk factors for intrauterine growth retardation among live births were investigated. From a total study group of 4578 consecutive live births, 76 (1.7%) infants were found to be growth retarded. These infants were then compared with a randomly selected control group of 76 term newborns with appropriate birthweight for their gestational ages. Delivery at term of a growth-retarded infant was significantly associated with maternal age under 20 years, maternal body mass index less than 23, first degree consanguinity, poor housing, primiparity, and inadequate prenatal care in univariate analysis. When considered jointly in multivariate logistic regression analysis, the significant determinants were reduced to primiparity, first degree consanguinity, and poor housing. These risk factors correctly predicted 63% and 71% of the intrauterine growth-retarded infants or normal birthweight infants, respectively.

Adult↗

PubMed2002

Screening extended families for genetic hemoglobin disorders in Pakistan.

BACKGROUND: We have investigated a strategy for identifying and counseling carriers of recessively inherited disorders in developing countries where consanguineous marriage is common. In such communities, gene variants are trapped within extended families, so that an affected child is a marker of a group at high genetic risk. METHODS: Fifteen large Pakistani families, 10 with a history of a hemoglobin disorder and 5 without any such history (controls), were screened for beta-thalassemia and abnormal hemoglobins. All carriers and married couples consisting of two carriers received counseling, and eight families have been followed for two years. RESULTS: In the control families, no carrier was found among 397 members tested. In the 10 families with an index case, 183 of 591 persons tested (31 percent) were carriers; carriers had a 25 percent risk of being in a marriage at risk for producing an affected child, and 17 of 214 married couples (8 percent) consisted of two carriers. No couple at risk was identified among 350 randomly selected pregnant women and their partners. All carriers reported that they have used the information provided in the testing and counseling process: carriers married to carriers with two or more healthy children have avoided further pregnancy, and most such couples with one or no healthy children have used prenatal diagnosis. Seven of eight new marriages and engagements are known not to be at risk. CONCLUSIONS: Testing of extended families is a feasible way of deploying DNA-based genetic screening in communities in which consanguineous marriage is common.

Anemia, Sickle Cell↗

PubMed1994

Cystic fibrosis and the liver--a Saudi experience.

Cystic fibrosis (CF) is an autosomal recessive disorder that is reported frequently among Caucasians. In view of the high rate of consanguinity in Saudi Arabia and the high number of children dying so young, many Saudi infants with CF remain undiagnosed owing to lack of clinical suspicion and proper diagnostic facilities. Over a 6-year period (1986-1992), we have made a diagnosis of CF in 36 cases. The aim of this report is to increase awareness of the hepatic presentation of CF in the developing word. Nine patients (25%) were originally referred to us as having liver disorders but subsequent investigations confirmed the diagnosis of CF. The referral diagnoses, number of patients in parentheses, were jaundice for investigation (four), glycogen storage disease (three), hepatomegaly for investigation (one) and neonatal hepatitis (one). Liver biopsies, obtained in five cases, demonstrated portal fibrosis and some steatosis. Consanguinity was present in eight cases, two were siblings. Four patients died. Three families had previously lost seven siblings during infancy with clinical features consistent with CF. It is concluded that hepatic presentation among Saudi patients with CF is relatively common, with serious sequelae.

Biopsy↗

PubMedDate not supplied

Risk factors for breast cancer in Pakistani women aged less than 45 years.

BACKGROUND: There has been an increase in the incidence of breast cancer in previously low-risk Asian countries. It is important to identify the risk factors for Asian women, as little information currently exists for this population. AIM: The objective of the study was to determine risk factors for breast cancer among Pakistani women. SUBJECTS AND METHODS: 498 cases younger than 45 years were interviewed from 1 July 1997 to 31 December 1998 at two major cancer hospitals. Age-matched population-based controls were selected from two cities and two villages to represent urban and rural areas. For the variables under study, cases and controls were compared by t-test. Conditional multiple logistic regression models were applied to the data set. RESULTS: Women with BMI >or= 30, with a family history of breast cancer and who were parous were at increased risk. Among parous women risk factors included BMI >or= 30, being in a consanguineous marriage, later age at menarche, later age at first full-term pregnancy, high parity and a history of abortion. CONCLUSION: The risk factors identified for Pakistani women below 45 years were similar to those observed in other studies. However, obesity in pre-menopausal women and late menarche were not protective and consanguinity was identified as a risk.

Abortion, Induced↗

PubMedDate not supplied

The effect of religious, cultural and social identity on population genetic structure among Muslims in Pakistan.

Knowledge of historical demography and contemporary social stratification can be valuable in understanding disease patterns, including genetic disorders, especially in communities that have a high prevalence of endogamous and/or consanguineous marriages. This paper provides a background to the religious, historical and socio-cultural factors that have helped define the bounds of endogamy for Muslims in undivided India and more specifically since the creation of Pakistan. The preference for endogamous marriage is based on the clan-oriented nature of the society, which values and actively seeks similarities in social group identity based on several factors, including religious, sectarian, ethnic, and tribal/clan affiliation. Religious affiliation is itself multi-layered and includes religious considerations other than being Muslim, such as sectarian identity (e.g. Shia or Sunni, etc.) and religious orientation within the sect (Isnashari, Ismaili, Ahmedi, etc.). Both ethnic affiliation (e.g. Sindhi, Baloch, Punjabi, etc.) and membership of specific biraderis or zat/quoms are additional integral components of social identity. Within the bounds of endogamy defined by the above parameters, close consanguineous unions are preferential due to a congruence of key features of group- and individual-level background factors.

Consanguinity↗

PubMedDate not supplied

The analysis of g-isonymy data.

g-Isonymy is defined to be generalized isonymy, and is taken to be two (or more) individuals who have the same surname (clan name) and who are related through marriage, although they are not necessarily married to one another. A general method for analysing g-isonymic data is proposed. It is shown how the random and non-random components of the frequency of g-isonymy can be obtained as well as the subcomponents due to preference for or against close consanguineous marriages and/or for or against remote consanguineous marriages. The proposed analysis, is applied to a subset of data on the Bhatias, a community which practises strict clan exogamy.

Consanguinity↗

PubMedDate not supplied

Isonymy structure of four Venezuelan states.

The isonymy structure of four Venezuelan States-Falcón, Mérida, Nueva Esparta and Yaracuy-was studied using the surnames of the Venezuelan register of electors updated in 1984. The surname distributions of 155 counties were obtained and, for each county, estimates of consanguinity due to random isonymy and Fisher's alpha were calculated. It was shown that for large sample sizes the inverse of Fisher's alpha is identical to the unbiased estimate of within-population random isonymy. A three-dimensional isometric surface plot was obtained for each State, based on the counties' random isonymy estimates. The highest estimates of random consanguinity were found in the States of Nueva Esparta and Mérida, while the lowest were found in Yaracuy. Other microdifferentiation indicators from the same data gave similar results, and an interpretation was attempted, based on the particular economic and geographic characteristics of each State. Four different genetic distances between all possible pairs of counties were calculated within States; geographic distance shows the highest correlations with random isonymy and Euclidean distance, with the exception of the State of Nueva Esparta, where there is no correlation between geographic distance and random isonymy. It was possible to group counties in clusters, from dendrograms based on Euclidean distance. Isonymy clustering was also consistent with socioeconomic and geographic characteristics of the counties.

Consanguinity↗

PubMedDate not supplied

Inbreeding incidence on biological fitness in an isolated mediterranean population: La Alta Alpujarra Oriental (southeastern Spain).

The incidence of parental inbreeding on biological fitness was analysed in a sample of the Alpujarrenian population. Fitness was estimated as the fertility and offspring viability from conception to reproductive age. The analysed sample represents about 45% of the population from the Alta Alpujarra Oriental in southeastern Spain, and includes 847 families and 2916 pregnancies. The results showed slightly higher reproduction in consanguineous marriages, but the differences observed were not statistically significant. Higher pregnancy numbers are usually interpreted as stemming from greater immunological compatibility of the mother and foetus and may also reflect the significantly higher early foetal viability in this population. According to other authors, the great number of births observed in Alpujarrenian consanguineous marriages is, in part, a reproductive compensation for increased perinatal and neonatal mortality found as a possible negative result of homozygous combinations of deleterious alleles.

Abortion, Spontaneous↗

PubMedDate not supplied

Population structure of two black Venezuelan populations studied through their mating structure and other related variables.

In order to obtain information about the population structure of two black Venezuelan populations with historical differences both in their origins and development, a variety of variables were utilized, especially on marital structure, including: frequency of surnames, isonymy, population genealogical consanguinity, multiple unions, and marital distances, all of which provided information and isolation, migration, endogamy, consanguinity, and patri-matrifocality. Results showed differences in the extent of isolation and endogamy, as well as differences in population structure, which can be directly related with historical conditions of each population. Results agree with those previously obtained with traditional genetic polymorphisms and with the historical information available. Thus, the usefulness of surnames for inferring about population structure is supported, as well as the usefulness of historical information for explaining genetic diversity.

Anthropology, Cultural↗

PubMed1998

Primary autosomal recessive microcephaly (MCPH1) maps to chromosome 8p22-pter.

Primary (or "true") microcephaly is inherited as an autosomal recessive trait and is thought to be genetically heterogeneous. Using autozygosity mapping, we have identified a genetic locus (MCPH1) for primary microcephaly, at chromosome 8p22-pter, in two consanguineous families of Pakistani origin. Our results indicate that the gene lies within a 13-cM region between the markers D8S1824 and D8S1825 (maximum multipoint LOD score of 8.1 at D8S277). In addition, we have demonstrated the genetic heterogeneity of this condition by analyzing a total of nine consanguineous families with primary microcephaly.

Chromosome Mapping↗

PubMed1999

Juvenile hemochromatosis locus maps to chromosome 1q.

Juvenile hemochromatosis (JH) is an autosomal recessive disorder that leads to severe iron loading in the 2d to 3d decade of life. Affected members in families with JH do not show linkage to chromosome 6p and do not have mutations in the HFE gene that lead to the common hereditary hemochromatosis. In this study we performed a genomewide search to map the JH locus in nine families: six consanguineous and three with multiple affected patients. This strategy allowed us to identify the JH locus on the long arm of chromosome 1. A maximum LOD score of 5.75 at a recombination fraction of 0 was detected with marker D1S498, and a LOD score of 5. 16 at a recombination fraction of 0 was detected for marker D1S2344. Homozygosity mapping in consanguineous families defined the limits of the candidate region in an approximately 4-cM interval between markers D1S442 and D1S2347. Analysis of genes mapped in this interval excluded obvious candidates. The JH locus does not correspond to the chromosomal localization of any known gene involved in iron metabolism. These findings provide a means to recognize, at an early age, patients in affected families. They also provide a starting point for the identification of the affected gene by positional cloning.

Adolescent↗

PubMed2000

Two new loci for autosomal recessive ichthyosis on chromosomes 3p21 and 19p12-q12 and evidence for further genetic heterogeneity.

Autosomal recessive ichthyosis (ARI) includes a heterogeneous group of disorders of keratinization characterized by desquamation over the whole body. Two forms largely limited to the skin have been defined: lamellar ichthyosis (LI) and nonbullous congenital ichthyosiform erythroderma (NCIE). A first gene for LI, transglutaminase TGM1, has been identified on chromosome 14, and a second one has been localized on chromosome 2. In a genomewide scan of nine large consanguineous families, using homozygosity mapping, two new loci for ARI were found, one for a lamellar form in a 6-cM interval on chromosome 19 and a second for an erythrodermic form in a 7.7-cM interval on chromosome 3. Linkage to one of the four loci could be demonstrated in more than half of 51 consanguineous families, most of them from the Mediterranean basin. All four loci could be excluded in the others, implying further genetic heterogeneity in this disorder. Multipoint linkage analysis gave maximal LOD scores of 11.25 at locus D19S566 and 8.53 at locus D3S3564.

Chromosome Mapping↗

PubMed2000

Prenatal and postnatal risk factors for mental retardation among children in Bangladesh.

This study evaluated the contribution of prenatal, perinatal, neonatal, and postnatal factors to the prevalence of cognitive disabilities among children aged 2-9 years in Bangladesh. A two-phase survey was implemented in 1987-1988 in which 10,299 children were screened for disability. In multivariate analyses, significant independent predictors of serious mental retardation in rural and urban areas included maternal goiter (rural odds ratio (OR) = 5.14, 95% confidence interval (CI): 1.23, 21.57; urban OR = 4.82, 95% CI: 2.73, 8.50) and postnatal brain infections (rural OR = 29.24, 95% CI: 7.17, 119.18; urban OR = 13.65, 95% CI: 4.69, 39.76). In rural areas, consanguinity (OR = 15.13, 95% CI: 3.08, 74.30) and landless agriculture (OR = 6.02, 95% CI: 1.16, 31.19) were also independently associated with the prevalence of serious mental retardation. In both rural and urban areas, independent risk factors for mild cognitive disabilities included maternal illiteracy (OR = 2.48, 95% CI: 0.86, 7.12), landlessness (OR = 4.27, 95% CI: 1.77, 10.29), maternal history of pregnancy loss (OR = 2.61, 95% CI: 0.95, 7.12), and small for gestational age at birth (OR = 3.86, 95% CI: 1.56, 9.55). Interventions likely to have the greatest impact on preventing cognitive disabilities among children in Bangladesh include expansion of existing iodine supplementation, maternal literacy, and poverty alleviation programs as well as prevention of intracranial infections and their consequences. Further population-based studies are needed to confirm and understand the association between consanguinity and serious cognitive disability.

Analysis of Variance↗

PubMed1997

Prelingual deafness: high prevalence of a 30delG mutation in the connexin 26 gene.

Prelingual non-syndromic (isolated) deafness is the most frequent hereditary sensory defect. In >80% of the cases, the mode of transmission is autosomal recessive. To date, 14 loci have been identified for the recessive forms (DFNB loci). For two of them, DFNB1 and DFNB2, the genes responsible have been characterized; they encode connexin 26 and myosin VIIA, respectively. In order to evaluate the extent to which the connexin 26 gene (Cx26) contributes to prelingual deafness, we searched for mutations in this gene in 65 affected Caucasian families originating from various countries, mainly tunisia, France, New Zealand and the UK. Six of these families are consanguineous, and deafness was shown to be linked to the DFNB1 locus, 10 are small non consanguineous families in which the segregation of the trait has been found to be compatible with the involvement of DFNB1, and in the remaining 49 families no linkage analysis has been performed. A total of 62 mutant alleles in 39 families were identified. Therefore, mutations in Cx26 represent a major cause of recessively inherited prelingual deafness since according to the present results they would underlie approximately half of the cases. In addition, one specific mutation, 30delG, accounts for the majority (approximately 70%) of the Cx26 mutant alleles. It is therefore one of the most frequent disease mutations so far identified. Several lines of evidence indicate that the high prevalence of the 30delG mutation arises from a mutation hot spot rather than from a founder effect. Genetic counseling for prelingual deafness has been so far considerably impaired by the difficulty in distinguishing genetic and non genetic deafness in families presenting with a single deaf child. Based on the results presented here, the development of a simple molecular test could be designed which should be of considerable help.

Australia↗

PubMed1997

Mapping of the familial infantile myasthenia (congenital myasthenic syndrome type Ia) gene to chromosome 17p with evidence of genetic homogeneity.

Familial infantile myasthenia is an autosomal recessive disorder, recently classified as congenital myasthenic syndrome type Ia. Onset of symptoms is at birth to early childhood with significant myasthenic weakness and possible respiratory distress, followed later in life by symptoms of mild to moderate myasthenia. Thirty-six patients of 12 families, seven of them consanguineous, were used to map the familial infantile myasthenia gene. A combination of linkage search through the genome, DNA pooling and homozygosity mapping were employed resulting in the localisation of this disease locus to the telomeric region of chromosome 17p. A maximum lod score of 9.28 at theta = 0.034 was obtained between the disease locus and marker locus D17S1537. Haplotype analysis showed all families to be consistent with linkage to this region thus providing evidence for genetic homogeneity of familial infantile myasthenia. Multipoint linkage analysis mapped the disease gene in the approximately 4.0 cM interval between marker loci D17S1537 and D17S1298 with a maximum multipoint lod score of 12.07. Haplotype analysis and homozygosity by descent in affected individuals of the consanguineous families revealed results in agreement with the confinement of the familial infantile myasthenia region within the interval between marker loci D17S1537 and D17S1298.

Chromosome Mapping↗