Autism: A Brief Diagnosis

Autism spectrum disorders (ASD) are a range of neurodevelopmental disorders that have been shown to have a basis in genetic etiology. Cytogenetic and linkage studies have been conducted to establish the genetic determinants of these disorders. Many neurodevelopmental disorders do often share the same genetic variances, so it has proven difficult to pinpoint areas relating specifically to autism spectrum disorder.

These disorders have been claimed to be genetically complex, as it is the end result of many different, seemingly insignificant genetic variants interacting with one another. However, rare chromosomal mutations, such as copy number variants (CNV), have also been found to contribute to the onset of ASD (Geschwind, D.H., 2011). If conferring specificity, association studies have found CNTNAP2 and RELN to be associated with autism. Some of the other more common chromosomal abnormalities observed in autistic patients include the 15q11-q13 maternal duplication, the 22q11 deletion, which is the most common of chromosomal aberrations and has been reported to be responsible for ADHD and schizophrenia, the 2q37 deletion and the 17p11.2 duplication (Kumar and Christian, 2009).

Scientists have yet to discover a set of biomarkers, either genetic or molecular, that can be used explicitly to diagnose ASD. There are, however, been studies conducted for the purpose of determining these biomarkers, in the hope that this could lead to earlier detection for the onset of these disorders. These studies have been relatively recent, but have revealed prospective inroads for the diagnosis of autism spectrum disorders. A set of biomarkers have been discovered through the protein profiling of blood plasma (Momeni, et. al., 2012), while another study has identified a gene expression profile based in the blood work of patients. This profile has also been consistent in the identification of autism spectrum disorders in children before the emergence of clinical signs (Glatt et. al., 2012).

It is unclear whether or not these findings have the potential to lead to a marketable blood test for autism, but it has been found that RNA derived from blood cells can be profiled for biomarkers in other mental illnesses, namely schizophrenia and bipolar disorder (Tsuang et. al., 2005). It is, as of yet, unknown if the identified biomarkers are definitively suggestive of pathogenesis of autism in the developing brain, and how these biomarkers are controlled and expressed.

Despite the amount of knowledge scientists have discovered about ASD, there are still many questions still left to be answered. As ASD is relatively heterogeneous when manifested in patients, an aligning of symptoms would be helpful with regard to the specific identification of biomarkers (Hu, V.W., 2012). A subphenotyping of ASD has been suggested, and this could be used in conjunction with studies being done over a range of age groups and times across early development to identify an even more precise group of biomarkers, resulting in a more tailored diagnosing process.

There is definitely the potential for blood related tests to be devised for the early diagnosis of ASD, but there are more developments to be made before any tests, blood related or otherwise, can be marketed to the wider public.

References

Geschwind, D.H. Genetics of autism spectrum disorders. Trends in Cognitive Sciences. 2011;15.9:409-416.

Glatt, S.J., Tsuang, M.T., Winn, M., Chandler, S.D., Collins, M., Lopez, L., Weinfield, M., Carter, C., Schork, N., Pierce, K., and Courchesne, E. Blood-Based Gene Expression Signatures of Infants and Toddlers With Autism. Journal of the American Academy of Child & Adolescent Psychiatry. 2012; 51.9: 934-944.

Hu, V.W. Subphenotype-dependent disease markers for diagnosis and personalized treatment of autism spectrum disorders. Disease Markers. 2012; 33:277-288.

Kumar, R.A. and Christian, S.L. Genetics of autism spectrum disorders. Current Neurology and Neuroscience Reports. 2009; 9:188-197.

Momeni, N., Bergquist, J., Brudin, L., Behina, F., Sivberg, B., Joghataei, M.T. and Persson, B.L. A novel blood-based biomarker for detection of autism spectrum disorders. Translational Psychiatry. 2012; 2:1-6.

Tsuang, M.T., Nossova, N., Yager, T., Tsuang, M., Guo, S., Shyu, K.G., Glatt, S.J. and Liew, C.C. Assessing the Validity of Blood-Based Gene Expression Profiles for the Classification of Schizophrenia and Bipolar Disorder: A Preliminary Report. American Journal of Medical Genetics Part B (Neuropsychiatric Genetics). 2006; 133:1-5.

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