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Unexpected inheritance of the (CGG)n trinucleotide expansion in a fragile X syndrome family.

The fragile X syndrome is the most frequent cause of inherited mental retardation. CGG repeat alleles are usually classified as normal, premutation, or full mutation based on the length of this triplet in the 5' untranslated region of the FMR1 gene. The pattern of inheritance follows a two-stage intergenerational process in which the premutation evolves into the full mutation. Some reverse mutations have been described, but they appear to be very rare. We describe a family in which a mother of two affected males herself carried a full mutation. Surprisingly, her clinically normal daughter, initially considered to be a carrier by linkage analysis, carried a very short premutation. Findings from our family study corroborate the hypothesis that the expansion during female transmission could be a postzygotic event and raise the problem of mosaicism.

Blotting, Southern↗

Tapeto-retinal degeneration in four Norwegian counties, II. Diagnostic evaluation of 407 relatives and genetic evaluation of 87 families.

In four Norwegian counties (fylker) 89 probands with tapeto-retinal degeneration have been traced and examined by the author. 407 of their nearest relatives (mostly first degree relatives) were also examined. A total of 63 of the relatives were found to be affected, of whom 42 had not been registered previously. After completion of the examinations the mode of inheritance differed from that previously estimated in 50% of the families. Of the 48 families with "classical" retinitis pigmentosa, 8% showed autosomal dominant, 50% autosomal recessive and 2% X-linked recessive inheritance. The remaining 40% were families with solitary cases without consanguinity between the parents of the affected person. Of five families with retinitis pigmentosa of pericentral type, four demonstrated an autosomal dominant pattern of inheritance.

Adolescent↗

The genetics of the Gilles de la Tourette syndrome: a review.

The Gilles de la Tourette syndrome (GTS) is a hereditary, neuropsychiatric-neurobehavioral disorder with childhood onset that is characterized by motor and vocal tics that may vary from relatively mild to very severe. The exact pathogenesis is still unknown. Following anecdotal reports of familial occurrence, systematic family studies have been carried out since 1980 to establish the mode of inheritance and ultimately to map and clone the susceptibility gene(s). Currently, as a result of combined North American, English, and Dutch studies, the most accepted genetic model is an autosomal dominant pattern of inheritance with incomplete penetrance and a variable expression. The objective of linkage studies is to "link" a particular DNA sequence (with known chromosomal localization) with the disease in all affected family members. Essential for these gene mapping studies is a clear and rigorous definition of the phenotype. Such studies are vastly more difficult if the disease phenotype is ambiguous, proper subject assignment being clouded by incomplete penetrance, cases mild enough to escape detection, or genetically unrelated but highly associated traits. Indeed, because of just these features, the initial optimism about the "well-defined and easy-to-objectivate" phenotype of GTS has gradually been tempered. The tics vary in frequency and severity, are frequently suppressed during examination, or might go unnoticed when associated behavioral symptoms like disturbed impulse control, obsessive-compulsive disorder and attention deficit disorder with hyperkinesia (among others) dominate the clinical picture. Whether these associated behavioral symptoms are a part of the phenotype remains to be established.(ABSTRACT TRUNCATED AT 250 WORDS)

Adoption↗

A new form of hypertrichosis inherited as an X-linked dominant trait.

A family with a distinct form of congenital generalized hypertrichosis was studied. Males were more severely affected than females, who exhibited asymmetric hair distribution. This finding was attributed to lyonization, since genealogical studies indicated an X-linked pattern of inheritance. A back mutation is postulated as the origin of this new phenotype.

Adolescent↗

Non-Mendelian mitochondrial inheritance as a cause of progressive genetic sensorineural hearing loss.

Awareness of non-Mendelian mitochondrial inheritance and of its role as an agent of genetic sensorineural hearing loss (SNHL) is recent. Mitochondria are passed on exclusively from the ovum to all the offspring of both sexes, a novel pattern of inheritance. Owing to the critical role of mitochondria in cellular energy metabolism, deletions or point mutations of the mitochondrial DNA often cause progressive SNHL and a variety of disorders in other organ systems (mitochondrial cytopathies). The clinical expression of mitochondrial diseases varies and depends on the proportion of mutated mitochondria in various body tissues, as well as the nature of the mutation or deletion. In order to determine how often SNHL occurs in mitochondrial diseases and what is its presenting symptom, and also whether SNHL is a marker for particular phenotypes, we carried out a review of published case reports of patients with an established diagnosis of mitochondrial disease. The review indicates that SNHL occurs at all ages and in virtually all variants of mitochondrial diseases. It is not clear whether SNHL is a marker for a more severe and more rapid course of disease; the lower prevalence of SNHL in descriptions of live patients than of those who had died may be an artifact of case selection reported in the literature. Mitochondrial disease needs to be considered in progressive hearing loss and better longitudinal audiometric study of established cases will be required to answer these questions.

Age of Onset↗

Inheritance of pancreatic cancer in pancreatic cancer-prone families.

Families are being increasingly recognized as carrying an inherited susceptibility for pancreatic cancer, apparently unrelated to any currently recognized syndrome. The authors provide a review of the current evidence for familial susceptibility to pancreatic cancer. A formal segregation analysis of the pattern of inheritance of pancreatic cancer in 70 families from the National Registry for Familial Pancreatic Cancer is described. This analysis suggests a single major gene with an autosomal dominant mode of inheritance controlling susceptibility for pancreatic cancer in these families.

Adenocarcinoma↗

Follicular atrophoderma with multiple basal cell carcinomas (Bazex).

Five patients from a single family are reported who have an inherited condition of which the main features are follicular atrophoderma, abnormalities of scalp hair and multiple basal cell carcinomas. Thes abnormalities are consistent with the syndrome described by Bazex et al. (1964). The pattern of inheritance of this condition is discussed.

Adult↗

Study of the pedigree of a patient with type 3 hyperlipoproteinaemia and sinking prebeta lipoprotein.

A 49-year-old woman, suffering from peripheral vascular disease, was found to have two lipoprotein abnormalities, namely, type III hyperlipoproteinaemia and sinking prebeta lipoprotein. Twenty-one members of the kindred were investigated in an attempt to determine the pattern of inheritance of both of these abnormalities. In a 21-year-old son of the proband plasma electrophoresis was in keeping with a type V hyperlipoproteinaemia. It is suggested that this may be a stage in the development of the characteristic type III pattern. If this is so it is consistent with previous suggestions of an incompletely penetrant single autosomal allele. Sinking prebeta lipoprotein was found in the plasma of two other members of the family. If this abnormality is also inherited as a single autosomal allele it must have a very low penetrance and the possibility that the abnormality is acquired cannot be excluded.

Adolescent↗

Bart syndrome with associated anomalies.

Bart syndrome is an inherited condition characterized by epidermolysis bullosa and congenital absence of skin. It has been associated with other anomalies including pyloric atresia. The genetic abnormality has been linked to chromosome 3, with an autosomal dominant pattern of inheritance. We present a case of Bart syndrome that was associated with pyloric atresia. The literature is reviewed pertaining to this unusual association. Recommendations are offered regarding genetic counseling and anticipatory guidance for affected families.

Abnormalities, Multiple↗

Ichthyosis follicularis with atrichia and photophobia (IFAP) syndrome in two unrelated female patients.

The IFAP syndrome is characterized by the congenital onset of ichthyosis follicularis, absence of hair, and photophobia. A limited number of patients with the disorder have been described, and X-linked recessive inheritance has been proposed. Two unrelated female patients with a complete IFAP syndrome are reported. Both patients show a diffuse distribution of the disorder without linear arrangement. Because the suggested X-linked recessive pattern of inheritance is unlikely in these patients, a different way of transmission or, alternatively, genetic heterogeneity of the disorder has to be considered.

Abnormalities, Multiple↗

Genetics of multiple sclerosis: determinants of autoimmunity and neurodegeneration.

Since the first description of multiple sclerosis (MS) as an inheritable disease by Eichhorst [1] accumulating epidemiological observations support a genetic hypothesis. Population, family and twin studies have revealed that Mendelian transmission of a single susceptibility gene would not be compatible with the observed patterns of inheritance. Like most other common diseases, MS is a complex trait, defined by several genes, each probably exerting a relatively small effect. Complex interactions among susceptibility genes and the environment are believed to contribute to a predisposition to dysregulation of inflammatory pathways, demyelination and tissue degeneration in the central nervous system (CNS). Natural history and pathological studies, however, define that MS represents a spectrum rather than a single entity of inflammatory demyelination. Despite a growing need for identifying molecular markers of biological subtypes of MS, only limited information is available for genotype-phenotype correlations. Four full genome scans using polymorphic microsatellite markers in nuclear and multiplex MS families indicated several chromosomal regions of susceptibility. With the recently discovered, highly abundant single nucleotide polymorphisms (SNPs) and family-based association methods, the means are now available to confine these relatively large regions of interest to candidate genes and susceptibility alleles. The currently available SNP maps favor indirect association studies based on linkage disequilibrium between marker and disease alleles. Here, we review available genetic data in MS, and introduce an additional strategy which correlate genetic markers with major biological components of the disease such as autoimmunity and neurodegeneration. This approach may yield important insights with utility in clinical practice.

Autoimmunity↗

Hypertension: genes and environment.

Hypertension can be classified as either Mendelian hypertension or essential hypertension, on the basis of the mode of inheritance. The Mendelian forms of hypertension develop as a result of a single gene defect, and as such are inherited in a simple Mendelian manner. In contrast, essential hypertension occurs as a consequence of a complex interplay of a number of genetic alterations and environmental factors, and therefore does not follow a clear pattern of inheritance, but exhibits familial aggregation of cases. In this review, we discuss recent advances in understanding the pathogenesis of both types of hypertension. We review the causal gene defects identified in several monogenic forms of hypertension, and we discuss their possible relevance to the development of essential hypertension. We describe the current approaches to identifying the genetic determinants of human essential hypertension and rat genetic models of hypertension, and summarise the results obtained to date using these methods. Finally, we discuss the significance of environmental factors, such as stress and diet, in the pathogenesis of hypertension, and we describe their interactions with specific hypertension susceptibility genes.

Animals↗

Auditory brainstem response patterns in familial and sporadic olivopontocerebellar atrophy.

Auditory brainstem responses (ABR) have been obtained in 22 patients, 15 with familial and 7 with sporadic olivopontocerebellar atrophy; 8 of them were pairs of siblings. ABR abnormalities have been found in 72.7%, with a significant higher percentage in familial versus sporadic patients. Similar ABR patterns have been obtained in affected members of the same family. No correlations have been found between ABR results and the following parameters: age, gender, disease duration, degree of clinical involvement and fashion of inheritance. ABR pattern did not show any modification over a follow-up period of 15-24 months. Our findings suggest that the involvement of the auditory pathways may be under genetic control.

Adult↗

Genetic anticipation and abnormal gender ratio at birth in familial primary pulmonary hypertension.

The genetic basis of familial primary pulmonary hypertension (FPPH) is unknown, but the clinical and pathologic features are the same as in sporadically occurring primary pulmonary hypertension (PPH). Because few families with this disease have been reported, the mode of inheritance and genetic features have not been clearly established. We previously reported a tendency for decreasing age of onset in subsequent generations of affected families. The purpose of this study was to examine the pattern of inheritance in a large number of families in an attempt to find clues to pathogenesis. From 24 families we studied 429 members, 124 of whom were known to carry the gene for disease. We constructed cumulative mortality curves for each gender of the 99 affected individuals. We analyzed gender ratios of progeny of affected members and carriers and compared age at death of affected members by generation. More females (160) than males (122) were born to persons carrying the gene, p < 0.01, suggesting selective wastage of male fetuses or an abnormal primary sex ratio. Genetic anticipation was confirmed; the age at death was 45.6 +/- 14.5 versus 36.3 +/- 12.6 versus 24.2 +/- 11 standard deviation (SD) years in successive generations, p < 0.05. Five cases of male-to-male transmission were observed, excluding X-linkage. Age at death was the same for males and females. More females had the gene (84 females, 40 males) and more females with the gene developed disease (72 of 84 females [86%] versus 27 of 40 males [68%]). The disease has highly variable penetrance among families.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[The NADPH-oxidase complex in chronic granulomatous disease: preliminary description of a cluster in Mérida-Venezuela].

Chronic Granulomatous Disease (CGD) is a primary immunodeficiency characterized by an unusual predisposition to develop bacterial and fungal infections due to a failure of phagocytic leukocytes to generate superoxide, required for the intracellular killing of microorganisms. The lack of superoxide production is secondary to a defect in the NADPH-oxidase enzymatic complex activation, as a result of mutations of any of the components. Both, X-linked and autosomal recessive patterns of inheritance have been demonstrated in this disease, being the X-linked the most frequent and characterized by mutations in gp91phox. Mutations in p47phox, p67phox and p22phox have been shown in the autosomal recessive pattern. The molecular and genetic characteristic of NADPH-oxidase complex and its pathology in CGD are reviewed along with a brief description of the preliminary findings in two families from Mérida, Venezuela.

Adolescent↗

Dominant inheritance in human cancer.

Familial aggregations of defined malignancies are of great importance for determining the genetic factors involved, as has been demonstrated for familial and sporadic retinoblastoma. In nearly all organs, neoplasms occur that are inherited similar to familial retinoblastoma (Rb). For example, more than 5% of all women suffering from breast cancer belong to breast cancer families in which the occurrence of the malignancy suggests an autosomal dominant pattern of inheritance. Familial colon cancer is associated with several well-known autosomal dominantly inherited polyposis syndromes, and also other susceptibilities without obvious clinical features. Site-specific cancers are often accompanied by other malignancies. In addition, there seem to be predispositions to a wider range of different, but well-defined neoplasms: e.g., adenocarcinomatosis of the colon and the endometrium, or the Li-Fraumeni/SBLA syndrome. The latter shows a spectrum of sarcoma, brain tumours, breast cancer, leukaemias, lung and adenocortical cancer. The genes leading to these types of dominantly inherited predispositions appear to be the tentatively so-called tumour suppressor genes, for which the Rb gene serves as a model. It manifests itself recessively on the level of the individual cell, which means both alleles must be deleted or inactivated before a retinoblast develops into a neoplastic cell. Clinical, epidemiological and molecular genetic studies have yet to establish whether the Rb model can be extended to all other forms of dominantly inherited human cancers.

Breast Neoplasms↗

Inheritance of white head spotting in natural populations of South American water rat (Nectomys squamipes Rodentia: Sigmodontinae).

Specimens with white head spots are present at low frequency in the natural populations of South American water rat (Nectomys squamipes) and absent in the sibling species Nectomys rattus. We analyzed the pattern of inheritance of the phenotype using complex segregation analysis of pedigrees of a captive-bred population of N. squamipes. We found that the inheritance of the white head spot in this species can be described within the framework of the major gene recessive model with incomplete penetrance of genotypes.

Animals↗

The genetics of primary nocturnal enuresis: inheritance and suggestion of a second major gene on chromosome 12q.

Primary nocturnal enuresis (PNE), or bedwetting at night, affects approximately 10% of 6 year old children. Genetic components contribute to the pathogenesis and recently one locus was assigned to chromosome 13q. We evaluated the genetic factors and the pattern of inheritance for PNE in 392 families. Dominant transmission was observed in 43% and an apparent recessive mode of inheritance was observed in 9% of the families. Among the 392 probands the ratio of males to females was 3:1 indicating sex linked or sex influenced factors. Linkage to candidate regions was tested in 16 larger families segregating for autosomal dominant PNE. A gene for PNE was excluded from chromosome 13q in 11 families, whereas linkage to the interval D13S263-D13S291 was suggested (Zmax = 2.1) in three families. Further linkage analyses excluded about 1/3 of the genome at a 10 cM resolution except the region around D12S80 on chromosome 12q that showed a positive two point lod score in six of the families (Zmax = 4.2). This locus remains suggestive because the material was not sufficiently large to give evidence for heterogeneity. Our pedigree analysis indicates that major genes are involved in a large proportion of PNE families and the linkage results suggest that such a gene is located on chromosome 12q.

Child↗