Genetics
Case-Control Family Study of Lesser Variant Traits in Autism
J. A. Wilcox, M. Tsaung, T, Schnurr, and N. Baida-Fragoso, Neuropsychobiology:2003; 47, 4: Proquest Medical Librar, Pages 171 - 177.
Family data were obtained from the relatives of 30 autistic patients, 30 patients with other pervasive developmental disorder and 30 healthy controls. Detailed interviewing was conducted to document any evidence of psychiatric illness of the family members of these probands. Anxiety disorders and obsessive-compulsive illness stood out as being closely associated with having autistic individuals in the family. The findings suggest that autism is a spectrum disorder that may be associated with anxiety and obsessive-compulsive illness. This type of association is consistent with a polygenic threshold effect for this group of conditions.
Defining the Broader Phenotype of Autism: Genetic, Brain, and Behavioural Perspectives
Geraldine Dawson, Sara Webb, Gerard D. Schellenberg, Stephen Dager, Seth Friedman, Elizabeth Aylward, and Todd Richards, Development and Psychopathology, 14 (2002), 581 - 611.
In this article, the current state knowledge of the cognitive neuroscience of social and language impairments in autism is reviewed. Following from this, six candidate broader phenotype autism traits are proposed: (a) face processing, including structural encoding of facial features and face movements, such as eye gaze; (b) social affiliation or sensitivity to social award, pertaining to the social motivational impairments found in autism; (c) motor imitation ability, particularly imitation of body actions; (d) memory, specifically those aspects of memory mediated by the medial temporal lobe - prefrontol circuits; (e) executive function, especially planning and flexibility; and (f) Language ability, particularly those aspects of language that overlap with specific language impairment, namely, phonological processing.
Nosological and Genetic Aspects of Asperger Syndrome
by Fred Volkmar, Ami Klin and David Pauls, (1998) Jr. Autism and Developmental Disorders, 28, 457-463.
In this preliminary report data were collected on 99 families and in 46% of families there was a positive family history of Asperger Syndrome or something very similar to it in first-degree relatives. High rates of disturbance were reported in both parents. As noted in Table II, high rates of difficulty (i.e. social difficulties), were observed, particularly with fathers. If a more restricted approach were used in which it appeared very probably that the parent clinically had AS or something very close to it the paternal predominance remains, albeit at a somewhat lower level (19% of fathers as opposed to 4% of mothers).
This study also provides some evidence for an etiological relationship between autism and AS, as 3.5% of siblings also had a diagnosis of autism.
Data from the study are consistent with the hypothesis that there is a broader phenotype of social and developmental difficulties in family members, for example, 33% of fathers and 14% of mothers were reported to have significant social difficulty…" (p. 460-461).
The Familial Aggregation of the Lesser Variant in Biological and Nonbiological Relatives of PDD Probands: a Family History Study
Satzmari, P, Maclean, J.E., Jones, M.B., Bryson, S.E., Zwaigenbaum, L., Bartolucci, G., Mahoney, W.J. and Tuff, L.
Objective: To determine the risk of the lesser variant (or PDD-like traits) in the biological and nonbiological second and third-degree relatives of PDD probands using a screening questionnaire and to investigate the extent to which the risk of the lesser variant differs according to various characteristics of the proband.
Method: The sample consists of a series of 34 nuclear families with 2 affected PDD children, 44 families with a single PDD child and 14 families who adopted a PDD child. Data on characteristics of the lesser variant in 1362 biological and 337 nonbiological second and third-degree relatives were collected from parents by telephone interview and from several maternal and paternal relatives by questionnaires.
Results: All components of the lesser variant were more common in biological relatives (BR) than nonbiological relatives (NBR) confirming the familial aggregation of the traits.
Discussion: These findings on familial aggregation are consistent with the suggestion that the genes for PDD also confer susceptibility to the lesser variant and that there may be reduced penetrance for these traits in females.
MPX nuclear families also had a higher risk of having a second or third-degree relative with the lesser variant than singleton families, indicating that the families with two or more affected siblings do appear to be “genetically loaded”.