VCFS is caused by a microdeletion in the long arm of chromosome 22. Psychotic symptoms develop in about one fourth of VCFS patients.3 Conversely, among patients with schizophrenia, Finn said, about 2% are estimated to have undiagnosed VCFS, and among those with childhood-onset schizophrenia or psychosis, about 6% are estimated to have undiagnosed VCFS.
While features of schizophrenia in patients with VCFS are not readily distinguishable from those of schizophrenia in patients without VCFS, according to Finn, a couple of differences do exist. Individuals with schizophrenia and VCFS are thought to have fewer negative symptoms but more adverse responses to atypical neuroleptics, including increased frequency of seizures.
Some other genetic disorders with psychiatric manifestations that can be tested for include fragile X syndrome, linked to learning disabilities, mood lability, and autistic-like behaviors; Smith-Magenis syndrome, a condition marked by mental retardation, distinctive facial features, sleep disturbances, and such problems as hyperactivity, anxiety, and explosive outbursts; Huntington disease, a progressive disorder that often begins with irritability, depression, small involuntary movements, poor coordination, and trouble learning new information or making decisions; and Wilson disease, the signs and symptoms of which can include clumsiness, trembling, difficulty in walking, speech problems, deteriorating school performance, depression, anxiety, and mood swings.
"When I see children with bipolar disorder, I am often running through the criteria for Smith-Magenis to see [whether] that is something I need to think about," Finn added.
While Huntington disease and other disorders are linked to a single gene, most cases of psychiatric illness are believed to be genetically complex, Finn said, so "we may not ever get a yes or no answer from testing."
Testing and counseling
Psychiatric disorders in most cases result from "multiple genes interacting with each other and interacting with environmental factors that, for the most part, we may not know about," she said. Consequently, genetic testing in psychiatry may be mostly about susceptibility and probabilistic test results. Patients may be told, for example, based on this combination of 8 genes, that they have a 50% chance of having schizophrenia develop.
Despite the complexity, most research studies suggest that patients, family members, and mental health clinicians are interested in genetic counseling and testing.1
Finn, who is affiliated with Harvard Medical School–Partners Healthcare Center for Genetics and Genomics and Massachusetts General Hospital, provides genetic counseling relevant to psychiatric disorders. She counsels people affected with psychiatric disorders who have questions about passing on illness to their children or who are thinking about using medications during pregnancy. She also counsels individuals who are planning to adopt a child with a family history of mental illness, as well as siblings and other relatives of affected individuals who have questions about their own risk or about risk to their children. Many times, Finn observed, siblings especially have not been able to talk with mental health professionals about risks and their experiences growing up with someone who has a psychiatric disorder. She uses the counseling opportunity to educate them about the disorder, including the typical symptoms, the usual course of illness, and treatment options.