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Overlaps between autism and language impairment: phenomimicry or shared etiology?

Bishop DV - Behav. Genet. (2010)

Bottom Line: Traditionally, autistic spectrum disorder (ASD) and specific language impairment (SLI) are regarded as distinct conditions with separate etiologies.Yet these disorders co-occur at above chance levels, suggesting shared etiology.A modified simulation involving G x G interactions obtained levels of comorbidity and rates of impairment in relatives more consistent with observed values.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK. dorothy.bishop@psy.ox.ac.uk

ABSTRACT
Traditionally, autistic spectrum disorder (ASD) and specific language impairment (SLI) are regarded as distinct conditions with separate etiologies. Yet these disorders co-occur at above chance levels, suggesting shared etiology. Simulations, however, show that additive pleiotropic genes cannot account for observed rates of language impairment in relatives, which are higher for probands with SLI than for those with ASD + language impairment. An alternative account is in terms of 'phenomimicry', i.e., language impairment in comorbid cases may be a consequence of ASD risk factors, and different from that seen in SLI. However, this cannot explain why molecular genetic studies have found a common risk genotype for ASD and SLI. This paper explores whether nonadditive genetic influences could account for both family and molecular findings. A modified simulation involving G x G interactions obtained levels of comorbidity and rates of impairment in relatives more consistent with observed values. The simulations further suggest that the shape of distributions of phenotypic trait scores for different genotypes may provide evidence of whether a gene is involved in epistasis.

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Related in: MedlinePlus

Phenomimicry model: the phenotype of autism spectrum disorder (ASD) can lead to language impairment (LI), but the resemblance with specific language impairment (SLI) is superficial and those with ASD+LI do not have risk factors for SLI
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Fig5: Phenomimicry model: the phenotype of autism spectrum disorder (ASD) can lead to language impairment (LI), but the resemblance with specific language impairment (SLI) is superficial and those with ASD+LI do not have risk factors for SLI

Mentions: A very different way of accounting for similar language problems in ASD and SLI is to argue that phenotypic continuities between conditions are more apparent than real, resulting from ‘phenomimicry’. I use this term to refer to the situation when the causal route for one disorder can lead to an outcome resembling the other disorder. Unlike ‘phenocopy’, which refers to an environmentally caused disorder that resembles a genetically-determined disorder, the term ‘phenomimicry’ makes no assumptions about whether etiology is genetic or environmental, or, as in this case, complex and multifactorial. It corresponds to what Neale and Kendler (1995) termed ‘multiformity’. In the case of ASD and SLI, this would mean that having a causal trait for one disorder could lead to a clinical picture resembling the other disorder. Figure 5 shows one version of phenomimicry where a child with ASD develops language deficits similar to those in SLI. The converse is also possible: a child with SLI might develop a clinical picture resembling ASD, perhaps because social interaction is difficult and stressful. Note that a phenomimicry account essentially is a variant of the traditional model (Fig. 1), and treats any phenotypic overlap between disorders as superficial.Fig. 5


Overlaps between autism and language impairment: phenomimicry or shared etiology?

Bishop DV - Behav. Genet. (2010)

Phenomimicry model: the phenotype of autism spectrum disorder (ASD) can lead to language impairment (LI), but the resemblance with specific language impairment (SLI) is superficial and those with ASD+LI do not have risk factors for SLI
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2921070&req=5

Fig5: Phenomimicry model: the phenotype of autism spectrum disorder (ASD) can lead to language impairment (LI), but the resemblance with specific language impairment (SLI) is superficial and those with ASD+LI do not have risk factors for SLI
Mentions: A very different way of accounting for similar language problems in ASD and SLI is to argue that phenotypic continuities between conditions are more apparent than real, resulting from ‘phenomimicry’. I use this term to refer to the situation when the causal route for one disorder can lead to an outcome resembling the other disorder. Unlike ‘phenocopy’, which refers to an environmentally caused disorder that resembles a genetically-determined disorder, the term ‘phenomimicry’ makes no assumptions about whether etiology is genetic or environmental, or, as in this case, complex and multifactorial. It corresponds to what Neale and Kendler (1995) termed ‘multiformity’. In the case of ASD and SLI, this would mean that having a causal trait for one disorder could lead to a clinical picture resembling the other disorder. Figure 5 shows one version of phenomimicry where a child with ASD develops language deficits similar to those in SLI. The converse is also possible: a child with SLI might develop a clinical picture resembling ASD, perhaps because social interaction is difficult and stressful. Note that a phenomimicry account essentially is a variant of the traditional model (Fig. 1), and treats any phenotypic overlap between disorders as superficial.Fig. 5

Bottom Line: Traditionally, autistic spectrum disorder (ASD) and specific language impairment (SLI) are regarded as distinct conditions with separate etiologies.Yet these disorders co-occur at above chance levels, suggesting shared etiology.A modified simulation involving G x G interactions obtained levels of comorbidity and rates of impairment in relatives more consistent with observed values.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK. dorothy.bishop@psy.ox.ac.uk

ABSTRACT
Traditionally, autistic spectrum disorder (ASD) and specific language impairment (SLI) are regarded as distinct conditions with separate etiologies. Yet these disorders co-occur at above chance levels, suggesting shared etiology. Simulations, however, show that additive pleiotropic genes cannot account for observed rates of language impairment in relatives, which are higher for probands with SLI than for those with ASD + language impairment. An alternative account is in terms of 'phenomimicry', i.e., language impairment in comorbid cases may be a consequence of ASD risk factors, and different from that seen in SLI. However, this cannot explain why molecular genetic studies have found a common risk genotype for ASD and SLI. This paper explores whether nonadditive genetic influences could account for both family and molecular findings. A modified simulation involving G x G interactions obtained levels of comorbidity and rates of impairment in relatives more consistent with observed values. The simulations further suggest that the shape of distributions of phenotypic trait scores for different genotypes may provide evidence of whether a gene is involved in epistasis.

Show MeSH
Related in: MedlinePlus