Abstracts

Rationale: Isodicentric chromosome 15 syndrome is a neurogenetic syndrome characterized by the presence of an extra structurally abnormal chromosome formed by inverted duplication of chromosome 15q11-13. This leads to an extra isodicentric 15 chromosome. Clinically, this results in epilepsy, hypotonia, minor dysmorphisms, moderate-severe developmental delay, and autistic behaviors. (1) Additionally, an increased risk of sudden and unexpected death has been reported in patients as young as seven years old, without clear cause. There is speculation that abnormalities of sleep, cardiorespiratory function, mitochondrial function, or epilepsy may be contributory, however there are few reports in the literature. We aim to determine the mechanism of sudden death in this patient population by reviewing patient data from our institution. Methods: Children with a diagnosis of isodicentric chromosome 15 syndrome and epilepsy were identified from our Neurology and Genetics Programs at Children’s Hospital Boston. Records were reviewed to identify subjects who also had sleep studies performed. Results: Sixteen children with isodicentric chromosome 15 syndrome were identified. Two of these children had sleep studies performed. Patient 1 had 29 central apneas of 7-50 seconds duration, associated with desaturations to as low as 70%. Most of these apneas were associated with either right or left anterior parasagittal onset of electrographic seizure, with eye deviation and tonic body stiffening accompanying them. Patient 2 had 11 brief central apneas of 10-25 seconds duration, not associated with desaturations below 95%. Frequent brief generalized electrographic seizures without central apneas or clinical accompaniment were also seen. Conclusions: The cause of sudden death in isodicentric chromosome 15 syndrome remains unclear. Our findings suggest that central sleep apnea associated with nocturnal seizures may be a potential explanation. Further understanding of nocturnal EEG and sleep patterns are required to explore this possibility. 1. Battaglia A. The inv dup(15) or idic(15) syndrome: a clinically recognisable neurogenetic disorder. Brain Dev. 2005 Aug;27(5):365-9.