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Familial essential tremor in 4 kindreds. Prospects for genetic mapping.

OBJECTIVES: To describe 4 large families with essential tremor (ET) to draw attention to the marked clinical heterogeneity of ET. To use computer simulation analysis to provide information about the power of the family material for future linkage studies. SUBJECTS: We examined a total of 251 members from 4 kindreds with ET. The mean (+/-SD) age at onset of ET varied among the 4 kindreds between 19.0 +/- 11.4 years and 45.6 +/- 7.4 years. Three of the kindreds had a total of 41 members with the combination of ET and dystonia, typically manifested as torticollis or dystonic writers' cramp. In 1 of the kindreds, ET seemed to be associated with malignant hyperthermia. One kindred represented "pure" ET without any associated disorders. METHODS: In addition to detailed clinical assessments, we conducted computer simulations on the families' pedigrees using a model that presumed an autosomal dominant inheritance pattern with high penetrance. RESULTS: Although there was evidence of clinical heterogeneity between the families, the duration of symptoms directly correlated with the severity of disease. The computer simulations indicated that 3 of the 4 pedigrees had enough power to generate a significant linkage result in a total genome search with highly polymorphic markers. CONCLUSIONS: This study confirms the frequent coexistence of ET and dystonia in individual families. Computer simulations can be used to determine the power of the family to detect a linked marker. Identification of the defective gene(s) will enable a better understanding and classification of these common movement disorders.

Aged↗

A gene for Parkinson disease.

Until recently, the possibility that genetic factors contributed significantly to the pathogenesis of Parkinson disease (PD) was accorded relatively short shift. Few patients with obviously familial PD are seen in common practice, and families with parkinsonism often present with rather atypical features. The discovery that the neurotoxin N-methyltetrahydropyridine (MPTP) rapidly induces an illness similar to sporadic PD added fuel to those arguing that environmental factors must be largely responsible. But more recently, this view has begun to shift because no generally plausible environmental factors emerged and data favoring a genetic component began to mount. Now it is clear that the cause of PD may on occasion be purely genetic and involve autosomal dominant as well as various other inheritance patterns. Moreover, it has become increasingly apparent that even in sporadic cases, the disease most likely reflects some combination of genetic susceptibility and environmental insult. In such instances, the genetic component presumably acts by increasing the vulnerability of dopamine-containing neurons in the nigrostriatal system to injury by 1 or more common, possibly by themselves relatively innocuous, environmental factors. This view has now been substantially reinforced and our ability to understand the pathogenesis of PD dramatically advanced by the recent identification of a gene responsible for PD in 4 unrelated families.

Environment↗

Clinical features and disease haplotypes of individuals with the N279K tau gene mutation: a comparison of the pallidopontonigral degeneration kindred and a French family.

BACKGROUND: An N279K missense mutation in exon 10 of the tau gene reported in an American family with pallidopontonigral degeneration (PPND family) was recently found in members of a French kindred with dementia and supranuclear palsy. OBJECTIVES: To compare clinical phenotypes of both families and to perform genealogical and molecular genetic studies to determine whether they are derived from a common founder. DESIGN AND METHODS: We performed clinical examinations of affected members of both families and compared clinical phenotypes, existing genealogical family records, and chromosome 17 microsatellite repeat markers in the vicinity of the tau gene. RESULTS: The inheritance pattern is autosomal dominant in the PPND family and appears so in the French family. Average age at onset of clinical symptoms was 43 years in the PPND family and 41 years in the French family. Mean disease duration was 8 years in the PPND family and 6 years in the French family. Parkinsonism, personality changes, and dementia of the frontotemporal type were seen in both kindreds. All affected patients exhibited rapidly progressive parkinsonism characterized by bradykinesia, tremor, postural instability, and rigidity. Some had a transient response to levodopa therapy during the initial stages. Pyramidal signs and eye movement abnormalities, including supranuclear gaze palsy, were common. Results of linkage studies of the tau region in chromosome 17 did not reveal a haplotype common to both kindreds. CONCLUSIONS: Affected members from both families had more clinical similarities than differences. Results of genealogical and molecular genetic studies determined that the families were not related. The N279K mutations found in both families have independent origins.

Adult↗

Frequency analysis and clinical characterization of spinocerebellar ataxia types 1, 2, 3, 6, and 7 in Korean patients.

BACKGROUND: By genetic analysis, the CAG repeat expansion has been established in spinocerebellar ataxia (SCA) types 1, 2, 3, 6, and 7. Despite the genetic differentiation of SCA, the characterization of the phenotypes of various SCAs has been challenging for better clinical diagnosis. OBJECTIVE: To analyze the frequencies and the clinical manifestations of SCA1, SCA2, SCA3, SCA6, and SCA7 in Korean patients. PATIENTS AND METHODS: We performed genetic analysis in 253 unrelated Korean patients with progressive cerebellar ataxia. We compared the frequencies, inheritance patterns, and various clinical manifestations of patients with genetically confirmed SCA. RESULTS: Among the 52 patients with expanded CAG repeat, the most frequent SCA type was SCA2, followed by SCA3, SCA6, SCA1, and SCA7. Nine patients (17%) had a negative family history of ataxia, mostly in SCA6. There were characteristic clinical features such as hypotonia and optic atrophy for SCA1; hyporeflexia for SCA2; nystagmus, bulging eye, and dystonia for SCA3; and macular degeneration for SCA7. Interestingly, 4 patients (1 with SCA2, 1 with SCA3, and 2 with SCA6) were misdiagnosed as having multiple-system atrophy because of the absence of family history and the presence of parkinsonism and urinary incontinence. CONCLUSIONS: This study provides a detailed analysis of the clinical characteristics of the genetically defined CAG-repeat SCAs in Korean patients. Although phenotypes were heterogeneous, some clinical features may be helpful for clinical diagnosis. However, genetic studies for SCA are needed despite uncertain family history or the presence of atypical clinical features causing misdiagnosis as atypical parkinsonism.

Adult↗

Molecular basis of low-penetrance retinoblastoma.

Retinoblastoma is a malignant tumor of the retina that occurs primarily in young children as a result of mutations in the retinoblastoma gene (RB), the first tumor suppressor gene to be identified. In about 35% to 40% of patients with retinoblastoma, an RB gene mutation is present in the germline, resulting in hereditary transmission of the disease. Most families with hereditary retinoblastoma demonstrate autosomal dominant inheritance with almost complete penetrance and high expressivity. However, some families display an inheritance pattern characterized by reduced penetrance and expressivity. Recent advances in our understanding of the structure and function of the retinoblastoma protein (pRB) now provide new insights into the molecular basis of this low-penetrance form of retinoblastoma. Low-penetrance retinoblastoma mutations either cause a reduction in the amount of normal pRB that is produced (class 1 mutations) or result in a partially functional mutant pRB (class 2 mutations).

Genes, Retinoblastoma↗

Hereditary congenital alacrima.

We describe a family with markedly deficient lacrimation from infancy and punctate corneal epithelial erosions. An autosomal dominant inheritance pattern is suggested. A hypoplasia of the lacrimal gland in this family was suggested by pharmacologic testing and by histopathologic examination of the lacrimal gland of the proposita. The family investigated in this report represents the first instance of hereditary congenital alacrima without associated ocular or adnexal abnormalities and apart from systemic disorders such as the Riley-Day syndrome and anhidrotic ectodermal dysplasia.

Adolescent↗

Visual field changes in cone-rod degenerations.

The visual field test results from 20 patients with con-rod degeneration (CRD) from all inheritance patterns were reviewed. Typical fundus findings of CRD included optic disc pseudoedema, temporal disc atrophy, parapapillary and disc telangiectasis, and few to no retinal pigmentary deposits. Visual field changes were seen to be distinctive and, like electrophysiologic tests, were helpful in pointing to a retinal degenerative process rather than an optic neuropathy.

Adolescent↗

Lattice corneal dystrophy type IIIA. Clinical and histopathologic correlations.

All three types of lattice corneal dystrophy are inherited and localized, and they largely involve linear corneal amyloid deposits. We encountered two white families with lattice corneal dystrophy which closely resembled type III. Four generations of one family and three of another family exhibited lattice corneal dystrophy. Because both families are from Caccamo, Sicily, Italy, we believe it is likely that both are from a single mutation. Thick, ropy lattice lines were seen to traverse the corneas almost from limbus to limbus and were easily detected with direct illumination. Histopathologic examination revealed accumulations of varying sized amyloid deposits in the stroma and ribbons of amyloid between the stroma and Bowman's layer typical of lattice corneal dystrophy type III. We have named the disease in this family lattice corneal dystrophy type IIIA, because of three differences from lattice corneal dystrophy type III: the presence of corneal erosions, the occurrence in whites, and the autosomal dominant inheritance pattern.

Aged↗

Fabry's disease in a black kindred.

In a 16-member black kindred with Fabry's disease, four hemizygous males had plasma alpha-galactosidase levels less than 6% and seven heterozygous females had plasma alpha-galactosidase levels between 10% and 50% of normal. A 16-year-old index male had hypertension with left ventricular hypertrophy, abnormal renal function, tortuous retinal veins, "myelin" inclusions in bone marrow macrophages, and intraepithelial inclusion bodies in the kidney. Scrotal angiectasia developed a year after diagnosis. The three other affected males had left ventricular hypertrophy and retinal vein tortuosity. Of the seven carrier females, five had frequent headaches, four had retinal vessel changes, three had proteinuria with normal renal function, and two had bundle-branch blocks on ECGs. There was no deuteranomalopia in this family, although the inheritance pattern of the Fabry gene is X-linked recessive.

Adolescent↗

Mapping of a gene for severe pediatric gastroesophageal reflux to chromosome 13q14.

CONTEXT: Gastroesophageal reflux (GER) has not previously been widely regarded as a hereditary disease. A few reports have suggested, however, that a genetic component may contribute to the incidence of GER, especially in its severe or chronic forms. OBJECTIVE: To identify a genetic locus that cosegregates with a severe pediatric GER phenotype in families with multiple affected members. DESIGN: A genome-wide scan of families affected by severe pediatric GER using polymorphic microsatellite markers spaced at an average of 8 centimorgans (cM), followed by haplotyping and by pairwise and multipoint linkage analyses. SETTING: General US community, with research performed in a university tertiary care hospital. SUBJECTS: Affected and unaffected family members from 5 families having multiple individuals affected by severe pediatric GER, identified through a patient support group. MAIN OUTCOME MEASURES: Determination of inheritance patterns and linkage of a genetic locus with the severe pediatric GER phenotype by logarithm-of-odds (lod) score analysis, considering a lod score of 3 or greater as evidence of linkage. RESULTS: In these families, severe pediatric GER followed an autosomal dominant hereditary pattern with high penetrance. A gene for severe pediatric GER was mapped to a 13-cM region on chromosome 13q between microsatellite markers D13S171 and D13S263. A maximum multifamily 2-point lod score of 5.58 and a maximum multifamily multipoint lod score of 7.15 were obtained for marker D13S1253 at map position 35 cM when presumptively affected persons were modeled as unknown (a maximum multipoint score of 4.88 was obtained when presumptively affected persons were modeled as unaffected). CONCLUSION: These data suggest that a gene for severe pediatric GER maps to chromosome 13q14. JAMA. 2000;284:325-334

Child↗

Mitochondrial anomalies in a Swiss family with autosomal dominant myoglobinuria.

We report on a Swiss family in which 10 individuals of both sexes in 4 successive generations suffered from myoglobinuria, precipitated by febrile illness. It is the second family described with autosomal dominant inheritance of myoglobinuria. Four individuals suffered acute renal failure, which in two was reversible only after dialysis. In a recent case, a mitochondrial disorder was suspected because of an abnormal increase in lactate levels during an exercise test and because of a subsarcolemmal accumulation of mitochondria in a muscle biopsy, associated with a lack of cytochrome C oxidase in some muscle fibers. No mutation in the mitochondrial DNA was identified. Along with the inheritance pattern, these findings suggest that the myoglobinuria in this family is caused by a nuclear-encoded mutation affecting the respiratory chain.

Adolescent↗

Familial paragangliomas: linkage to chromosome 11q23 and clinical implications.

Familial paragangliomas (PGL), or glomus tumors, are slow-growing, highly vascular, generally benign neoplasms usually of the head and neck that arise from neural crest cells. This rare autosomal-dominant disorder is highly penetrant and influenced by genomic imprinting through paternal transmission. Timely detection of these tumors affords the affected individual the opportunity to avoid the potential morbidity associated with surgical removal, and mortality that may accompany local and distant metastases. Linkage to two distinct chromosomal loci, 11q13.1 and 11q22.3-q23, has been reported, suggesting heterogeneity. We evaluated three multigenerational families with hereditary PGL, including 19 affected, and 59 unaffected and potentially at-risk individuals. Numerous microsatellite markers corresponding to each candidate region were tested in all members of the three families. Confirmation of linkage to 11q23 was established in all three families. The inheritance pattern was consistent with genetic imprinting. Using these data, we were able to provide presymptomatic diagnosis with subsequent removal of tumor from one individual, and to start several others on an MRI surveillance protocol.

Adolescent↗

Unusual autosomal recessive lymphatic anomalies in two unrelated Amish families.

We report on two unrelated Amish families with familial occurrence of unusual lymphatic anomalies. The first family had two children, a boy and a girl, with congenital chylothorax both of whom died as a consequence of this condition (one prenatally and one neonatally). The second family has two brothers with isolated cystic hygroma. Neither family has any other individuals affected with any type of lymphatic anomaly. Differential diagnosis and presumed autosomal recessive inheritance pattern will be discussed. Familial cystic hygroma not associated with hydrops fetalis and neonatal death has not been reported previously.

Chylothorax↗

Apparently new syndrome of sensorineural hearing loss, retinal pigment epithelium lesions, and discolored teeth.

We report on a family with early-onset sensorineural hearing loss, abnormal retinal pigment epithelium granularity, accumulation of creamy-white lesions at the level of the retinal pigment epithelium particularly superior to the arcade, and selective discoloration (brown) of molars or canine deciduous teeth that follows an apparent autosomal recessive inheritance pattern. This appears to be a new syndrome that can be distinguished from the known otodental, oculo-acoustic and flecked retina syndromes by the occurrence of distinct dental and ocular abnormalities.

Child, Preschool↗

Lack of evidence of a major gene acting on postaxial polydactyly in South America.

Data on polydactyly were obtained from two large samples: the Latin American Collaborative Study of Congenital Malformations (ECLAMC), and from a migrant Northeastern Brazilian population of rural origin (Hospedaria). ECLAMC is a case-control clinical epidemiological program comprising 10,035 individuals distributed among 2,030 segregating nuclear families. Hospedaria data consisted of 6,586 examined individuals belonging to 1,040 nuclear families. Using complex segregation analysis methodology we found no evidence of two loci (a major gene and a modifier locus) acting on postaxial polydactyly in the present study. Very high heritability values (in a classical multifactorial model) of postaxial polydactyly were detected, for several sets of analyses in ECLAMC and in Hospedaria. For the whole ECLAMC sample there is a peculiar suggestion of a major recessive gene effect responsible for the trait; however, no comparison with a model involving transmission probabilities (tau) was possible in this highly heterogeneous sample. If the whole ECLAMC sample is divided in subsamples, according to Black admixture proportions, the same multifactorial picture emerges. Two different inheritance patterns were verified for hand (HP) and foot (FP) postaxial polydactyly: For HP there is evidence of a non-Mendelian transmission mechanism, while for FP the parental/sib transmission appears to be due only to multifactorial causes.

Brazil↗

Genetic epidemiological study of schizophrenia in Palau, Micronesia: prevalence and familiality.

We are studying the genetic etiology of schizophrenia in the Republic of Palau, a remote island nation in Micronesia that has been geographically and ethnically isolated for approximately 2,000 years. The first epidemiological phase sought to estimate the lifetime prevalence of schizophrenia and evaluate the familiality of the illness based on complete ascertainment of cases and families segregating schizophrenia. A total of 160 strictly defined cases of schizophrenia were ascertained in a population of 13,750 adults who were 15 years of age and older. The lifetime prevalence of strictly defined schizophrenia in Palau was 1.99% overall and 2.77% in males vs. 1.24% in females. This greater than 2:1 male-to-female risk ratio for schizophrenia was accompanied by an earlier mean age of onset for males (23.3 years) than for females (27.5 years). These 160 cases of strict schizophrenia represent 59 separate families each identified by a single common founder. Eleven of these families have 5 to 14 cases and represent nearly half of the strict schizophrenia cases in Palau. Although schizophrenia is clearly aggregating in these 11 families, cases are distributed sparsely throughout the large sibships. In the entire sample of 160 cases of strict schizophrenia, there were only 11 sib-pairs and 2 sib-trios. When a family was defined to include third-degree relatives, only 11 cases (6.9%) were nonfamilial. The majority of the ascertained cases can be linked together into extended pedigrees with complex multilineal inheritance patterns. These intricately interconnected families may pose challenges for traditional linkage techniques. However, these Palauan families represent a valuable resource for studying the genetic etiology of schizophrenia because there may be fewer susceptibility genes for schizophrenia in this genetic isolate than in the heterogeneous populations that are common throughout the world today.

Adolescent↗

Mental retardation and seizure disorder in Schimke immunoosseous dysplasia.

Schimke immunoosseous dysplasia (SID) is a rare, pleiotropic disorder compromising spondyloepiphyseal dysplasia, nephrotic syndrome, defective T-cell-mediated immunity, and vascular changes which can lead to cerebral infarcts. The cause is unknown but an autosomal recessive inheritance pattern has been suggested. Understanding of the clinical phenotype is evolving; however, the neurologic spectrum is not well known. We report on a 17-year-old woman who presented with behavior changes, developmental regression, and partial complex seizures in early childhood. Computed tomographic scan of the brain was normal at that time. Short stature and cognitive deficits became evident several months later. At 4 1/2 years, she developed nephrotic syndrome and later malignant hypertension. Recent magnetic resonance imaging of the brain showed focal encephalomalacia in the parietal regions and a magnetic resonance angiography documented narrowing of the middle cerebral arteries. A skeletal survey showed evidence of spondyloepiphyseal dysplasia. We have not been able to identify an immune defect. To our knowledge this is the first reported patient with SID, profound mental retardation, and a seizure disorder. This case supports the theory that an intrinsic vascular defect may be more important in the pathogenesis of SID than a T-cell-mediated immune deficit.

Abnormalities, Multiple↗

Diagnosis of von Willebrand disease type 2N: a simplified method for measurement of factor VIII binding to von Willebrand factor.

Diagnosis of von Willebrand disease Type 2N (vWD 2N), which mimics hemophilia A and its carrier state, is important for accurate genetic counseling and appropriate therapy. To make testing for the disorder more clinically applicable, we developed a simplified method for measurement of factor VIII (FVIII) binding to von Willebrand factor (vWF) using commercially available reagents and standard clinical assays. FVIII binding to vWF was measured by capture of patient vWF by polyclonal antibodies on cyanogen bromide-activated Sepharose beads, reaction with recombinant FVIII, and assay of unbound FVIII by clotting methods. Unbound vWF was measured in patient plasma after capture by the Laurell method. The ratio of bound FVIII/bound vWF was normal in hemophilia A, vWD Type 1, and vWD Type 3 patients, and abnormal in 5 subjects from two families, all of whom had vWD 2N mutations. Patient 1, with FVIII 8 U/dl, vWF: Ag 61 U/dl, vWF:RC 74 U/dl, and FVIII binding nil, was homozygous for the Arg91 Gln mutation. She was followed during pregnancy and delivered an unaffected heterozygous son. Patient 2 had FVIII 8 U/dl, vWF:Ag 73 U/dl, and vWF:RC 71 U/dl, and very low FVIII binding. She was heterozygous for Arg91Gln, as were her mother and sister; no second vWD 2N mutation was found. Her brother, with FVIII 14 U/dl, vWF:Ag 113 U/dl, and vWF:RC 72 U/dl, has no evidence of vWD 2N. With an X-linked inheritance pattern of bleeding tendency, this family is the first reported with combined hemophilia A and vWD 2N.

Adult↗