Background
Segmental duplications at breakpoints (BP4–BP5) of chromosome 15q13.2q13.3 mediate a recurrent genomic imbalance syndrome associated with mental retardation, epilepsy, and/or EEG abnormalities.
Patients
DNA samples from 1,445 unrelated patients submitted consecutively for clinical array comparative genomic hybridisation (CGH) testing at Children’s Hospital Boston and DNA samples from 1,441 individuals with Autism from 751 families in the Autism Genetic Resource Exchange (AGRE) repository.
Results
We report the clinical features of five patients with a BP4-BP5 deletion, three with a BP4–BP5 duplication, and two with an overlapping but smaller duplication identified by whole genome high resolution oligonucleotide array CGH. These BP4–BP5 deletion cases exhibit minor dysmorphic features, significant expressive language deficits, and a spectrum of neuropsychiatric impairments that include autism spectrum disorder, ADHD, anxiety disorder, and mood disorder. Cognitive impairment varied from moderate mental retardation to normal IQ with learning disability. BP4–BP5 covers ~1.5Mb (chr15:28.719–30.298Mb) and includes 6 reference genes and 1 miRNA gene, while the smaller duplications cover ~500 kb (chr15:28.902–29.404 Mb) and contain 3 reference genes and one miRNA gene. The BP4–BP5 deletion and duplication events span CHRNA7, a candidate gene for seizures. However, none of these individuals reported here have epilepsy, although two have an abnormal EEG.
Conclusions
The phenotype of chromosome 15q13.2q13.3 BP4–BP5 microdeletion/duplication syndrome may include features of autism spectrum disorder, a variety of neuropsychiatric disorders, and cognitive impairment. Recognition of this broader phenotype has implications for clinical diagnostic testing and efforts to understand the underlying etiology of this syndrome.
The data suggest that children with bruxism have a higher arousal index, which may be associated with an increased incidence of attention-behavior problems. Future studies investigating pediatric sleep bruxism will need to focus on behavior issues that may be prevalent in this population.
The association between gray matter heterotopias and seizures is well established; whether seizures originate from these lesions is not known. We evaluated three patients with intractable complex partial seizures and periventricular nodular heterotopias (PNHs) with video-EEG monitoring with multiple depth electrodes, including placement in the PNH, to determine whether seizures originate from the PNH. In two of the three patients, all seizures arose from the PNH as low-voltage beta activity. In the third patient, 80% arose from the hippocampi and 20% from the heterotopia. PNHs may serve as an epileptogenic focus in patients with intractable epilepsy.
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