The purpose of genetic testing is to provide a genetic diagnosis and to provide as much information as possible to patients and families. First, the information may explain why a child, in this case, has a disorder. Understanding the cause of a disorder is helpful to many families. Second, if the testing reveals a known condition it may provide information about prognosis. Some conditions are associated with various health conditions or behavioral profiles, or levels of functioning. It allows the team and family to prepare, and when possible prevent an adverse outcome. Third, in some cases, the results provide information on recurrence risk. Families may want to have an estimate of the chances another child could be similarly affected. Finally, as we learn more about what the genes do, specific treatments may become available to normalize the biochemical internal environment, if not the gene itself.
The findings of a genetics evaluation are becoming more and more complex and interesting. A new concept, copy number variant (CNV), has entered the vocabulary. It refers to the phenomenon that individuals may have bits of chromosomes that are missing, duplicated, rearranged, or in other ways different from the usual. The phenomenon was uncovered through the Human Genome Project. We did, in the past, think that this was invariably a serious problem for the individual. However, with the new tools available, it turns out that many apparently normal folks have CNV, as it is abbreviated. It is not at all rare. What is not clear is why some CNVs are associated with specific or general problems and others are not. One hypothesis is the size of the CNV that is important. Another hypothesis is the specific bit of DNA that is duplicated or deleted. Certain areas of the genome are more susceptible to CNV than other areas. We often have clinical conditions associated with these CNVs. So, William syndrome and DiGeorge syndrome are CNVs. However, the correlation between the size of the deletion and the symptoms is not high.
Another complication is that the same CNV may be associated with different clinical conditions. So, for example, duplication of Chromosome 15 q11-13 is associated with cognitive impairment, autism, and schizophrenia. What accounts for variation in the phenotype is also still unclear. Another complication is that a CNV may be detected and yet be irrelevant to the child’s condition. The geneticists may need to run a control sample. The parents may be asked to provide a blood sample too. So, the information revealed by genetics testing may not clarify and may actually confuse parents.
At this point, historically, we do not know the implications of many of the abnormalities now uncovered through new testing methods. Some families may have heightened worries about genetics testing. With so much unknown, it is unclear whether the best course of action is to avoid the testing altogether or to seek professional and parent-to-parent support if an abnormality is detected. I vote for support. It is through the testing that we will eventually learn what we need to know.Final issue: The results of genetic testing do not change the child, only our understanding of the child’s condition. The child’s educational, behavioral, and therapuetic programs rarely change based on the results. More importantly, the need for good parenting and all that it entails –love, education, discipline, support –remain essential, whether the child has a genetic variation or not.
[Heidi Feldman is the Ballinger-Swindells Professor of Developmental and Behavioral Pediatrics at Standford University School of Medicine. She is also the Medical Director of the Development and Behavior Unit at Lucille Packard Children’s Hospital. Dr. Feldman has a long-standing research interest in child speech and language. She has published research on childhood apraxia of speech, typical and atypical child language, the developmental implications of otitis media with effusion, children with neuronal injuries and language learning, and the delivery of health care to children with special health care needs. She is a member of the Professional Advisory Board of the Childhood Apraxia of Speech Association of North America.]