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”.