The prevalence of severe mental retardation (SMR) was studied in one of the 24 suburban municipalities in Stockholm. The study area had a high proportion of non-European nationals. The study population comprised 14138 children born between 1979 and 1992 who resided in this municipality on the census day, 31 December 1995. The total prevalence of SMR was 4.5 per 1000, being 3.7 per 1000 and 5.9 per 1000 in the European and in the non-European population, respectively. The majority of cases (66%) had a definite prenatal origin. Down syndrome was the cause in 20%. Six families (10%) had at least two children with SMR. It was concluded that the prevalence was higher than in previous Swedish studies. Many cases were attributed to genetic factors. Consanguineous marriages were assumed to be a factor of importance in the distribution of aetiologies. Demographic differences between areas in Sweden must be considered when planning habilitation services.
This is a continuation of a series of papers devoted to studying the genetic mechanisms of adaptation in migrants from isolated highland populations of Dagestan to new ecological conditions (lowlands). This paper describes the main results of studying the relationship between levels of inbreeding, homozygosity, and physiological sensitivity. Earlier, we found that decreased resistance to changing environmental factors in migrants to lowlands from the Dagestan highlands was connected with their high level of homozygosity. The data obtained allow us to assume that missing links in this chain of events include, in addition to parameters of inbreeding level, parameters of neurophysiological sensitivity, including absolute and differential sensitivity of various analyzers sensory systems, which are from 65 to 75% genetically determined. Migrants from highland auls (villages) to lowlands exhibited a decreased rate of sensomotor reactions in response to light and sound of various intensities, as well as decreased differential color sensitivity in the long-, medium-, and short-wave ranges of the spectrum, compared to highlanders. The results suggest the selective mortality of migrants from highlands to lowlands during adaptation to new conditions. Those migrants who dies were characterized by specific gene complexes that determined the characteristic features of expression of a number of interrelated polymorphic and quantitative traits. Thus, the high levels of homozygosity and inbreeding were accompanied by a greater neurophysiological sensitivity and lower indices of body weight and height.
Hereditary factors of arterial hypertension were evaluated genetically and epidemiologically in the study of an isolated population of Dagestan with high inbreeding. High prevalence of arterial hypertension was found. Its highest morbidity was found in native population of Tukhums characterized also by the highest inbreeding.
Allgrove syndrome (isolated glucocorticoid deficiency, achalasia and alacrima) was found in eight members of an inbred French Canadian/North American Indian pedigree. The high degree of consanguinity supports an autosomal recessive mode of inheritance for this disorder. Six patients presented with hypoglycaemia and other evidence of cortisol deficiency between 2.5 and 8 years of age; however, two others became cortisol deficient after initial testing showed normal cortisol responses to ACTH, evidence that the glucocorticoid insufficiency of this syndrome may not be congenital, but may develop as late as the third decade. No evidence of mineralocorticoid deficiency has been found during 65 patient-years of follow-up. Alacrima was the earliest and most consistent clinical sign of Allgrove syndrome. Other manifestations of peripheral or autonomic neuropathy were found in four patients. The patients showed similar facial features, and three had significant velo-pharyngeal incompetence. All showed oesophageal dysmotility even in the absence of symptomatic dysphagia. In-vitro studies of lymphocyte ACTH binding showed no differences from normal controls. If such lymphocyte binding, as has been suggested, reflects adrenal ACTH receptor activity, these data would suggest that the glucocorticoid deficiency of Allgrove syndrome is not the result of a defect in that receptor. However, the observation that ACTH does not elicit increased adenylate cyclase activity even in normal lymphocytes casts considerable doubt on the physiological significance of ACTH binding to lymphocytes. It seems likely, therefore, that true ACTH receptors are not expressed on peripheral lymphocytes, and any conclusions regarding a possible receptor defect in Allgrove syndrome must await studies of receptor expression on adrenal cell membranes.
Previous studies have reported that related human couples tend to produce more children than unrelated couples but have been unable to determine whether this difference is biological or stems from socioeconomic variables. Our results, drawn from all known couples of the Icelandic population born between 1800 and 1965, show a significant positive association between kinship and fertility, with the greatest reproductive success observed for couples related at the level of third and fourth cousins. Owing to the relative socioeconomic homogeneity of Icelanders, and the observation of highly significant differences in the fertility of couples separated by very fine intervals of kinship, we conclude that this association is likely to have a biological basis.
Comment In: Science. 2008 May 30;320(5880):1160-118511672
Andermann syndrome or Agenesis of the Corpus Callosum with Polyneuropathy (MIM 218000) is an autosomal recessive disease almost exclusively found in Québec. Only few cases have been reported in other populations. The locus for Andermann syndrome was assigned to chromosome 15q13-q15 in French Canadian families. We performed a haplotype analysis with two markers of this chromosomal region in an Algerian consanguineous family with two affected sibs. The children were homozygous for both markers, suggesting genetic homogeneity in Andermann syndrome.
The genetics of primary angle-closure glaucome (a.c.g.) was studied: a) through the prevalence in sibs and children of a.c.g. probands, and b) through the family distribution of the closely correlated axial anterior chamber depth (ACD). The material emerged from an epidemiologic study in Greeland Eskimos. a) Compared with the general population, the observed prevalence of a.c.g. was increased in sibs of a.c.g. probands and the estimated, future prevalence was found to be the same in sibs and children. Age influence prevented a proper Mendelian analysis, but no simple monogenic inheritance seems probable. b) The biometric study showed a relatively shallow chamber in sibs, children, nephews, nieces and grandchildren of a.c.g. probands. Regression analyses revealed a corresponding pattern, also in control families of probands with shallow chambers and in general population families. A heritability of 70% was found, indicating that about two thirds of the age and sex independent variation in ACD seems to be genetic.