Febrile convulsions in a national cohort followed up from birth. II--Medical history and intellectual ability at 5 years of age.

Three hundred and three children with febrile convulsions were identified in a national birth cohort of 13 135 children followed up from birth to the age of 5 years. Breech delivery (p less than 0.05) was the only significantly associated prenatal or perinatal factor. There were no associations with socioeconomic factors. Excluding the 13 known to be neurologically abnormal before their first febrile convulsion, children who had had a febrile convulsion did not differ at age 5 from their peers who had not had febrile convulsions in their behaviour, height, head circumference, or performance in simple intellectual tests.     

Etiologic heterogeneity in the familial aggregation of congenital cardiovascular malformations.

Recent data indicate that there is increased risk of congenital cardiovascular malformations (CCVM) within families of probands diagnosed with congenital cardiovascular malformations that are due to altered embryonic blood flow (flow lesions). In the present study, regressive models recently developed by Bonney were used to compare specific models of inheritance and to test for etiologic heterogeneity among three subgroups of 375 flow-lesion families identified by the Baltimore-Washington Infant Study. When all families were analyzed as a single group, the best-fitting model was a simple recessive model with Mendelian transmission; race did not have a significant effect on estimated risk. Separate analyses of families of probands with left heart defects, right heart defects, and ventricular septal defects (VSD) confirmed this simple Mendelian recessive model as the model of choice. However, when race was included as a covariate in these genetic models, there was evidence for significant heterogeneity among the three subgroups. There was an increased risk to relatives of white probands with right heart defects and to relatives of black probands with VSD, while there was no effect of race among relatives of probands with left heart defects. These results strongly suggest that there is etiologic heterogeneity in the control of CCVM among flow-lesion families and that the patterns of familial aggregation differ among the races.     

Genetic epidemiology of rheumatoid arthritis.

We conducted family studies and segregation analyses of rheumatoid arthritis (RA) that were based on consecutive patients with RA ascertained without regard to family history or known risk factors. First-degree relatives from 135 simplex and 30 multiplex families were included in the analyses. A highly penetrant recessive major gene, with a mutant allele frequency of .005, was identified as the most parsimonious genetic risk factor. Significant evidence for heterogeneity in risk for RA was observed for proband gender but not for proband age at onset. Kaplan-Meier risk analysis demonstrated significant evidence for differences in the distribution of risk among first-degree relatives. These analyses demonstrated that both proband gender and age at onset are important risk factors but that proband gender appears to be the more important determinant of risk, with relatives of male probands having the greatest cumulative risk for RA. In addition, log-linear modeling identified proband gender, familiality (multiplex or simplex), and an interaction term between these two variables as being adequate to define the distribution of risk in families. The pattern of risk for RA among susceptible individuals and its inheritance is thus heterogeneous. For future genetic analyses, families with an excess of affected males having a young age at onset may be the most informative in identifying the putative recessive gene and its modifiers.     

Febrile convulsions in a national cohort followed up from birth. I--Prevalence and recurrence in the first five years of life.

Of 13 135 children followed up from birth to the age of 5 years, 303 (2.3%) had febrile convulsions. Prior neurological abnormality had been noted in 13. Of the 290 remaining children, 57 (20%) presented with a complex convulsion, and 103 children (35%) went on to have further febrile convulsions. The risk of further febrile convulsions varied with the age at first convulsion and the presence of a history of convulsive disorders in relatives. There were no significant differences between the sexes.     

Segregation analysis of schizophrenia and related disorders

Segregation analysis was applied to 79 nuclear families ascertained through chronic schizophrenic probands. Analysis was performed on the diagnosis of schizophrenia alone and on schizophrenia and schizotypal personality disorder (milder phenotype) combined. The models used were the transmission probability model and the mixed model. Because the disease is associated with reduced fertility, all likelihoods were calculated conditional on parental phenotypes. However, compatibility of the mating-type distribution predicted by each model with the observed was also examined. In all analyses, results suggested consistency with genetic transmission. In the analysis of schizophrenia alone, discrimination among models was difficult. In the analysis including the milder phenotypes, all single-locus models without polygenic background were excluded, while pure polygenic inheritance could not be eliminated. The polygenic model also gave good agreement with supplementary observations (lifetime disease incidences, mating-type distribution, and monozygotic twin concordance). The estimated components of variance for the polygenic model were: polygenes (H) 81.9%; common sib environment (B) 6.9%; random environment (R) 11.2%. Although the polygenic model was parsimonious, segregation analysis and the supplementary observations were also consistent with a mixed model, with a single major locus making a large contribution to genetic liability. Such a locus is more likely to be recessive than dominant, with a high gene frequency and low penetrance. The most likely recessive mixed model gave the following partition of liability variance: major locus, 62.9%; polygenes, 19.5%; common sib environment, 6.6%; and random environment, 11.0%.     

Primary immunisation and febrile convulsions in Oxford 1972-5.

A three-year study of febrile convulsions in Oxford with comprehensive notification from general practice and hospitals showed a 3% risk for all children of suffering at least one febrile convulsion by the age of 5 years. Children were most at risk between 6 and 27 months, and febrile convulsions were most likely to be prolonged in children aged 9-15 months. The association between febrile convulsions and primary immunisations in the preceding 28 days was compared in case and control children, matched for age and sex. Results suggested that such association was a chance relationship with age. If association was direct, the febrile convulsion rates per 1000 immunisation doses were estimated as follows: diphtheria, pertussis, tetanus--0-09 per 1000; poliomyelitis--0-6 per 1000; and measles--0-9 per 1000. Hence if any of these vaccines had a secific causal relationship with febrile convulsions, these rates would probably have been much higher.     

Genetic aspects of febrile convulsions

Summary A total of 6706 children 3 years of age (3491 boys, 3215 girls) in a particular geographical area in Fuchu (population approximately 182 000), Tokyo, was investigated. Some 654 children (9.8%; 10.5% for male, 9.0% for female) had had at least one convulsion, and the incidence of febrile convulsions was 6.7% (7.2% for male, 6.2% for female). The 450 FC children with febrile convulsions and 620 randomly selected control children were analyzed on the mode of inheritance.The incidence of the disease among siblings was 21.9% (29.7% after age correction), which rose greatly with increasing numbers of affected family members, and the segregation ratio among siblings was higher (36.5%) with one FC parent, and lower (18.5%) if neither parent had had a seizure. The more severe the illness in FC children, the larger the incidence among siblings.Population and family studies indicated that heredity plays an important role in febrile convulsions and that multifactorial inheritance is most likely.     

Mode of inheritance of nonsyndromic cleft lip with or without cleft palate: a reanalysis.

Nonsyndromic cleft lip with or without cleft palate (CL +/- P) is traditionally recognized as a multifactorial threshold trait (MFT). Recently, however, evidence for the involvement of a major gene in the etiology of CL +/- P has been reported. To assess the potential for major-gene involvement in the etiology of this trait, familial recurrence patterns from several family studies of CL +/- P were reanalyzed. The recurrence patterns in first-degree relatives of CL +/- P probands were found to be compatible with the expectations for either an MFT or a generalized single-major-locus (gSML) trait. The use of multiple thresholds based on proband sex, defect bilaterality, or palatal involvement did not help to discriminate between these models. However, the pattern of recurrence among MZ twins and more remote relatives of CL +/- P probands is not consistent with gSML inheritance but is compatible with either an MFT model or a model specifying multiple interacting loci. For such a model, no single locus can account for more than a sixfold increase in risk to first-degree relatives. These findings have important implications with regard to the feasibility of detecting linkage to loci conferring susceptibility to CL +/- P.     

A major gene for primary hypoalphalipoproteinemia.

Sixteen kindreds were ascertained through probands clinically determined to have primary hypoalphalipoproteinemia, characterized by bottom decile high-density lipoprotein cholesterol (HDL-c), but otherwise normolipidemic. Age- and sex-adjusted, standardized HDL-c levels on 64 individuals in 14 nuclear families in which the proband was a parent were analyzed using the unified mixed model of segregation analysis as implemented in the computer program POINTER. The analysis proceeded by using the likelihood of offspring conditional on the parental phenotypes (conditional likelihood), which appears to overcome the limitation of possible heterogeneity in the selection criteria and provides an appropriate correction for the ascertainment. In these families, the multifactorial contribution to the phenotype appears to be small and significant only in the offspring generation. Although it was not possible to resolve the dominance pattern at the major locus since none of a recessive, additive, or dominant hypothesis could be firmly rejected, these families provided clear evidence for a major gene. Genetic heterogeneity is still a possibility, even within "primary" hypoalphalipoproteinemia.     

Complex segregation analysis of autism.

A complex segregation analysis of autism in 185 Utah families was carried out using the mixed model. The 209 affected individuals in these families represent nearly complete ascertainment of the autistic cases born in Utah between 1965 and 1984. The sibling recurrence risk for autism was 4.5% (95% confidence limits 2.8%-6.2%). Likelihoods were maximized for major-gene models, a polygenic model, a sibling-effect model, and a mixed model consisting of major-gene and shared-sibling effects. The analysis provided no evidence for major-locus inheritance of autism. Subdivision of the sample according to the probands' IQ levels showed that sibling recurrence risk did not vary consistently with IQ level. A segregation analysis of families in which the proband had an IQ less than 50 also failed to provide evidence for a major locus. However, because of the etiologic heterogeneity of this disorder, genetic analysis of other meaningful subsets of families could prove informative.     

Complex segregation analysis provides compelling evidence for a major gene underlying obsessive-compulsive disorder and for heterogeneity by sex

Evidence from twin and family studies supports a genetic etiology for obsessive-compulsive disorder (OCD). The purpose of this study was to test whether a major gene is implicated in a proportion of families with OCD. Complex segregation analyses of 153 families (80 case and 73 control), ascertained in the Johns Hopkins OCD Family Study, provided strong evidence for a major gene. A Mendelian-dominant model, with significant sex effects and with residual familial effects, best explained the observed data. Stratification of the sample by the sex of probands provided further evidence of heterogeneity with respect to familial aggregation. Segregation analyses of 86 families with a female proband and of the 67 families with a male proband suggested that a Mendelian-dominant model with familial residual effects was the most parsimonious model explaining the inheritance of OCD in both subgroups.     

Complex segregation analysis of non-myoclonic idiopathic generalized epilepsy in families ascertained from probands affected with idiopathic epilepsy with tonic-clonic seizures in Antioquia,Colombia

In an attempt to identify the possible role of major genes, multifactorial inheritance, and cohort effects in the susceptibility to idiopathic epilepsy with generalized tonic-clonic seizures of the awakening type (GTCS), complex segregation analysis was performed in 196 nuclear families ascertained through affected probands with idiopathic epilepsy with GTCS belonging to the Paisa community of Antioquia (Colombia). Models postulating no transmission, single major locus (dominant and recessive) only, and multifactorial component only, were rejected. Since the codominant single major locus model could not be rejected and models that assign no major locus to transmission, no polygenic component to transmission, and no transmission of the major effect were rejected, complex segregation analysis suggested that a major autosomal codominant allele together with a multifactorial component (mixed model) best explained clustering of idiopathic epilepsy with GTCS in families of the Paisa community. The deficit of transmission of heterozygotes (0.17) is compatible with the existence of epistasis acting on a major gene whose frequency was estimated to be 0.0211. Its transmission variance accounts for 81% of the susceptibility to idiopathic epilepsy with GTCS. The complementary variance (19%) is due to the polygenic component. Received: 19 January 1996 / Revised: 11 March 1996     

Occult pneumococcal bacteraemia and febrile convulsions.

Over two years 29 children had bacteraemia due to Streptococcus pneumoniae at this hospital. In 15 previously healthy children the site of infection could not be identified, and in most of them, bacteraemia was not suspected clinically. All 15 had high total white cell (greater than or equal to 17 x 10(9)/1) and neutrophil (greater than or equal to 11 x 10(9)/1) counts. Twelve children were under 4 years of age, and of these, 10 had been admitted because of a simple febrile convulsion and one had a prolonged febrile convulsion. Occult pneumococcal bacteraemia has been reported in the USA for more than 10 years, but no series has been reported from the United Kingdom. Occult pneumococcal bacteraemia may be an important cause of febrile convulsions. Persisting bacteraemia and the development of focal infections, including pneumococcal meningitis, have been reported. Meningitis did not occur after occult bacteraemia in our patients. Studies to date have been retrospective, and thus the true incidence of the complications and the best treatment are not clear. A prospective study of children with febrile convulsions could provide answers.     

Familial clustering of rheumatoid arthritis with other autoimmune diseases

Previous studies have shown that rheumatoid arthritis aggregates within families. However, no formal genetic analysis of rheumatoid arthritis in pedigrees together with other autoimmune diseases has been reported. We hypothesized that there are genetic factors in common in rheumatoid arthritis and other autoimmune diseases. Results of odds-ratio regression and complex segregation analysis in a sample of 43 Caucasian pedigrees ascertained through a rheumatoid arthritis proband or matched control proband, revealed a very strong genetic influence on the occurrence of both rheumatoid arthritis and other autoimmune diseases. In an analysis of rheumatoid arthritis alone, only one inter-class measure, parent–sibling, resulted in positive evidence of aggregation. However, three inter-class measures (parent–sibling, sibling–offspring, and parent–offspring pairs) showed significant evidence of familial aggregation with odds-ratio regression analysis of rheumatoid arthritis together with all other autoimmune diseases. Segregation analysis of rheumatoid arthritis alone revealed that the mixed model, including both polygenic and major gene components, was the most parsimonious. Similarly, segregation analysis of rheumatoid arthritis together with other autoimmune diseases revealed that a mixed model fitted the data significantly better than either major gene or polygenic models. These results were consistent with a previous study which concluded that several genes, including one with a major effect, is responsible for rheumatoid arthritis in families. Our data showed that this conclusion also held when the phenotype was defined as rheumatoid arthritis and/or other autoimmune diseases, suggesting that several major autoimmune diseases result from pleiotropic effects of a single major gene on a polygenic background. Received: 12 January 1998 / Accepted: 10 June 1998     

Segregation analysis reveals evidence of a major gene for Alzheimer disease.

In an attempt to resolve the relative influences of major genes, multifactorial heritability, and cohort effects on the susceptibility to Alzheimer disease (AD), complex segregation analysis was performed on 232 nuclear families. All families were consecutively ascertained through a single proband who was referred for diagnostic evaluation of a memory disorder. The results suggest that susceptibility to AD is determined, in part, by a major autosomal dominant allele with an additional multifactorial component. Single-locus, polygenic, sporadic, and no-transmission models, as well as recessive inheritance of the major effect, were significantly rejected. Excess transmission from the heterozygote was marginally significant and probably reflects the presence of phenocopies or perhaps the existence of two or more major loci for AD. The frequency of the AD susceptibility allele was estimated to be .038, but the major locus accounts for only 24% of the transmission variance, indicating a substantial role for other genetic and nongenetic mechanisms in the causation of AD.     

Comparison of spontaneous and idoxuridine-induced micronuclei by chromosome painting

Fluorescence in situ hybridisation (FISH) technique with chromosome specific library (CSL) DNA probes for all human chromosomes were used to study about 9000 micronuclei (MN) in normal and idoxuridine (IUdR)-treated lymphocyte cultures of female and male donors. In addition, MN rates and structural chromosome aberrations were scored in Giemsa-stained chromosome spreads of these cultures. IUdR treatment (40 microg/ml) induced on the average a 12-fold increase of the MN rate. Metaphase analysis revealed no distinct increase of chromosome breaks but a preferential decondensation at chromosome 9q12 (28-79%) and to a lower extend at 1q12 (8-21%). Application of FISH technique with CSL probes to one male and one female untreated proband showed that all human chromosomes except chromosome 12 (and to a striking high frequency chromosomes 9, X and Y) occurred in spontaneous MN. In cultures containing IUdR, the chromosomal spectrum found in MN was reduced to 10 chromosomes in the male and 13 in the female proband. Eight chromosomes (2, 6, 12, 13, 14, 15, 17 and 18) did not occur in MN of both probands. On the contrary chromosomes 1 and especially 9 were found much more frequently in the MN of IUdR-treated cultures than in MN of control cultures. DAPI-staining revealed heterochromatin signals in most of the IUdR-induced MN. In an additional study, spontaneous and IUdR-induced MN were investigated in lymphocytes of another female donor using CSL probes only for chromosomes 1, 6, 9, 15, 16 and X. The results confirmed the previous finding that chromosomes 1 and 9 occur very often in MN after IUdR-treatment. The results indicate that decondensation of heterochromatic regions on chromosomes 1 and 9 caused by IUdR treatment strongly correlates with MN formation by these chromosomes.     

Evidence for major gene inheritance of Alzheimer disease in families of patients with and without apolipoprotein E epsilon 4.

Apolipoprotein E (APOE) genotype is the single most important determinant to the common form of Alzheimer disease (AD) yet identified. Several studies show that family history of AD is not entirely accounted for by APOE genotype. Also, there is evidence for an interaction between APOE genotype and gender. We carried out a complex segregation analysis in 636 nuclear families of consecutively ascertained and rigorously diagnosed probands in the Multi-Institutional Research in Alzheimer Genetic Epidemiology study in order to derive models of disease transmission which account for the influences of APOE genotype of the proband and gender. In the total group of families, models postulating sporadic occurrence, no major gene effect, random environmental transmission, and Mendelian inheritance were rejected. Transmission of AD in families of probands with at least one epsilon 4 allele best fit a dominant model. Moreover, single gene inheritance best explained clustering of the disorder in families of probands lacking epsilon 4, but a more complex genetic model or multiple genetic models may ultimately account for risk in this group of families. Our results also suggest that susceptibility to AD differs between men and women regardless of the proband's APOE status. Assuming a dominant model, AD appears to be completely penetrant in women, whereas only 62%-65% of men with predisposing genotypes develop AD. However, parameter estimates from the arbitrary major gene model suggests that AD is expressed dominantly in women and additively in men. These observations, taken together with epidemiologic data, are consistent with the hypothesis of an interaction between genes and other biological factors affecting disease susceptibility.     

A novel SCN1A mutation associated with generalized epilepsy with febrile seizures plus--and prevalence of variants in patients with epilepsy

We recently described mutations of the neuronal sodium-channel alpha-subunit gene, SCN1A, on chromosome 2q24 in two families with generalized epilepsy with febrile seizures plus (GEFS+) type 2. To assess the contribution that SCN1A makes to other types of epilepsy, 226 patients with either juvenile myoclonic epilepsy, absence epilepsy, or febrile convulsions were screened by conformation-sensitive gel electrophoresis and manual sequencing of variants; the sample included 165 probands from multiplex families and 61 sporadic cases. The novel mutation W1204R was identified in a family with GEFS+. Seven other coding changes were observed; three of these are potential disease-causing mutations. Two common haplotypes, with frequencies of .67 and .33, were defined by five single-nucleotide polymorphisms (SNPs) spanning a 14-kb region of linkage disequilibrium. An SNP located 18 bp upstream of the splice-acceptor site for exon 3 was observed in 7 of the 226 patients but was not present in 185 controls, suggesting possible association with a disease mutation. This work has confirmed the role of SCN1A in GEFS+, by identification of a novel mutation in a previously undescribed family. Although a few candidate disease alleles were identified, the patient survey suggests that SCN1A is not a major contributor to idiopathic generalized epilepsy. The SCN1A haplotypes and SNPs identified here will be useful in future association and linkage studies.     

Serum and cerebrospinal fluid nitrite/nitrate levels in patients with rotavirus gastroenteritis induced convulsion

Nitric oxide (NO) is a highly reactive free radical that is involved in a variety of different biological process. In recent reports, the putative role of NO in the neuropathogenesis of brain inflammation has been demonstrated. And then the relation between neuronal NO and convulsive seizures induced by virus has been suggested. However, there are few reports about NO in vivo under viral neurological infections. In order to evaluate the relation between NO production and neurological disorders induced by viral infection, sixty-six cases including 11 patients with rotavirus gastroenteritis admitted for convulsions were examined in this study. NO metabolites (NOx) levels in both serum and cerebrospinal fluid obtained from rotavirus gastroenteritis patients with convulsion were much higher than in those of patients with purulent meningitis, encephalitis, febrile convulsion or in the control group. There was a relative correlation between IL-6 and NOx in some cases. These results indicated that NO may have a pathophysiological role in convulsions associated by rotavirus infection either through indirect or direct effects of NO. Consequently, NOx inhibitors might be helpful for the treatment of rotavirus encephalopathy.     

Failure of phenobarbitone to prevent febrile convulsions.

One-hundred-sixty-five children without known neurological disorder who presented with their first febrile convulsion between the ages of six months and three years were assigned to daily phenobarbitone treatment or to a control group and followed up at a special clinic for six months. One-hundred-and-sixty-one-one children completed the trial, and of the 88 children assigned to phenobarbitone treatment 10 had further convulsions during this period compared with 14 of the 73 control children. Only 49 of those assigned to phenobarbitone took the drug regularly throughout the trial, and four of these had further febrile convulsions, a proportion not significantly different from that in the controls. All four had mean plasma phenobarbitone concentrations over 69 mumol/l (16 mug/ml) during the trial and in three the plasma concentration was at or over this figure within eight hours over 69 mumol/l (16 mug/ml) during the trial and in three the plasma concentration was at or over this figure within eight hours of the repeat convulsion. Regular phenobarbitone does not seem to prevent febrile convulsions. Attention should instead be directed to organising emergency services to allow early termination of fevrile convulsions, whether first or subsequent, to prevent irreversible brain damage.