Application of array-based comparative genome hybridization in children with developmental delay or mental retardation

22q13 Microduplication Syndrome in Siblings with Mild Clinical Phenotype: Broadening the Clinical and Behavioral Spectrum

Distal duplication 22q (22q13.3qter) is a rare condition with only 24 cases described so far. Parental balanced reciprocal translocations and pericentric inversions involving chromosome 22 predispose to the conception of an unbalanced offspring and are more frequently reported than de novo events. The clinical phenotype of patients is highly variable and does not necessarily correlate with the extent of the duplicated segment. Short stature, microcephaly, hypertelorism, cleft lip or palate, low-set ears, and intellectual disability seem to be the most consistent features. Familial reoccurrence is extremely rarely reported. Here, we report 2 siblings with a 22q13.3qter duplication detected by array CGH; their mother is a carrier of a pericentric inversion in chromosome 22. Their relatively mild phenotype and identical chromosomal breakpoints as well as duplication size are unique. This is the first case described so far.

A case of isodicentric chromosome 15 presented with epilepsy and developmental delay

We report a case of isodicentric chromosome 15 (idic(15) chromosome), the presence of which resulted in uncontrolled seizures, including epileptic spasms, tonic seizures, and global developmental delay. A 10-month-old female infant was referred to our pediatric neurology clinic because of uncontrolled seizures and global developmental delay. She had generalized tonic-clonic seizures since 7 months of age. At referral, she could not control her head and presented with generalized hypotonia. Her brain magnetic resonance imaging scans and metabolic evaluation results were normal. Routine karyotyping indicated the presence of a supernumerary marker chromosome of unknown origin (47, XX +mar). An array-comparative genomic hybridization (CGH) analysis revealed amplification from 15q11.1 to 15q13.1. Subsequent fluorescence in situ hybridization analysis confirmed a idic(15) chromosome. Array-CGH analysis has the advantage in determining the unknown origin of a supernumerary marker chromosome, and could be a useful method for the genetic diagnosis of epilepsy syndromes associated with various chromosomal aberrations.

Copy number variations in patients with electrical status epilepticus in sleep

Electrical status epilepticus in sleep syndrome is the association of the electroencephalographic pattern and deficits in language or global cognitive function and behavioral problems. The etiology is often unknown, but genetic risk factors have been implicated. Array-based comparative genomic hybridization was used to identify copy number variations in 13 children with electrical status epilepticus in sleep syndrome to identify possible underlying risk factors. Seven copy number variations were detected in 4 of the 13 patients, which consisted of 6 novel gains and 1 loss, the recurrent 15q13.3 microdeletion. Two patients carried a probable pathogenic copy number variation containing a gene involved in the cholinergic pathway. Genetic aberrations in patients with electrical status epilepticus in sleep syndrome can provide an entry in the investigation of the etiology of electrical status epilepticus in sleep. However, further studies are needed to confirm our findings.

The Developmental-Behavioral Pediatrics Research Network: another step in the development of the field

Developmental-behavioral pediatrics was formally recognized as a subspecialty of pediatrics in 1999 with one of the goals being to promote research in the field. However, research has generally been a small component of most developmental-behavioral pediatricians' activities. In an effort to expand research in the field, the Developmental-Behavioral Pediatrics Research Network (DBPNet) was funded through a cooperative agreement with the Health Resources and Services Administration, Maternal Child Health Bureau. This funding supports the development of an infrastructure to support multisite research that aims to optimize the health and functional status of children with developmental and behavioral concerns and disorders. This article describes the need for a developmental-behavioral pediatrics research network, the development of the infrastructure for DBPNet, and the mechanisms for investigators to collaborate with the Network.

Microarray analysis in children with developmental disorder or epilepsy

The technique of chromosomal microarray analysis identifies genetic imbalance. Evaluation of its diagnostic role in pediatrics is still underway. We describe our experience with chromosomal microarrays. We retrospectively reviewed the charts of children in the Sections of Neurology and Clinical Genetics at St. Christopher's Hospital for Children who had undergone microarray analysis between 2006 and 2009. Collected data included age, sex, and the presence of mental retardation, developmental delay, autism, learning disability, hypotonia, dysmorphic features, and epilepsy, and the use of microarray technique. Statistical analysis was performed using SPSS. There were 82 children (mean age ± S.D., 5.7 ± 5 years), including 45 (55%) boys and 37 (45%) girls. All patients exhibited a normal karyotype. Microarray analysis produced abnormal results in 20 (23.5%). Deletions comprised 74% of all abnormalities. Patients with ≥ 4 clinical variables demonstrated a 30.5% incidence of abnormal chromosomal microarray findings, compared with 8.7% of patients with ≤ 3 clinical variables (P = 0.039, χ(2) test). Logistic regression indicated that motor impairment (P = 0.039) and presence of epilepsy (P = 0.024) independently contributed to the model. The likelihood of an abnormal microarray result increased with the number of clinical abnormalities. Microarray analysis will likely become the diagnostic genetic test of choice in children with neurodevelopmental disorders or epilepsy.

Clinically detectable copy number variations in a Canadian catchment population of schizophrenia

Copy number variation (CNV) is a highly topical area of research in schizophrenia, but the clinical relevance is uncertain and the translation to clinical practice is under-studied. There is a paucity of research involving truly community-based samples of schizophrenia and widely available laboratory techniques. Our objective was to determine the prevalence of clinically detectable CNVs in a community sample of schizophrenia, while mimicking typical clinical practice conditions. We used a brief clinical screening protocol for developmental features in adults with schizophrenia for identifying individuals with 22q11.2 deletions and karyotypically detectable chromosomal anomalies in 204 consecutive patients with schizophrenia from a single Canadian catchment area. Twenty-seven (13.2%) subjects met clinical criteria for a possible syndrome, and 26 of these individuals received clinical genetic testing. Five of these, representing 2.5% of the total sample (95% CI: 0.3%-4.6%), including two of ten patients with mental retardation, had clinically detectable anomalies: two 22q11.2 deletions (1.0%), one 47, XYY, and two other novel CNVs--an 8p23.3-p23.1 deletion and a de novo 19p13.3-p13.2 duplication. The results support the utility of screening and genetic testing to identify genetic syndromes in adults with schizophrenia in clinical practice. Identifying large, rare CNVs (particularly 22q11.2 deletions) can lead to significant changes in management, follow-up, and genetic counselling that are helpful to the patient, family, and clinicians.

Value for money? Array genomic hybridization for diagnostic testing for genetic causes of intellectual disability

Array genomic hybridization (AGH) provides a higher detection rate than does conventional cytogenetic testing when searching for chromosomal imbalance causing intellectual disability (ID). AGH is more costly than conventional cytogenetic testing, and it remains unclear whether AGH provides good value for money. Decision analytic modeling was used to evaluate the trade-off between costs, clinical effectiveness, and benefit of an AGH testing strategy compared to a conventional testing strategy. The trade-off between cost and effectiveness was expressed via the incremental cost-effectiveness ratio. Probabilistic sensitivity analysis was performed via Monte Carlo simulation. The baseline AGH testing strategy led to an average cost increase of $217 (95% CI $172-$261) per patient and an additional 8.2 diagnoses in every 100 tested (0.082; 95% CI 0.044-0.119). The mean incremental cost per additional diagnosis was $2646 (95% CI $1619-$5296). Probabilistic sensitivity analysis demonstrated that there was a 95% probability that AGH would be cost effective if decision makers were willing to pay $4550 for an additional diagnosis. Our model suggests that using AGH instead of conventional karyotyping for most ID patients provides good value for money. Deterministic sensitivity analysis found that employing AGH after first-line cytogenetic testing had proven uninformative did not provide good value for money when compared to using AGH as first-line testing.

"Idiopathic" mental retardation and new chromosomal abnormalities

Mental retardation is a heterogeneous condition, affecting 1-3% of general population. In the last few years, several emerging clinical entities have been described, due to the advent of newest genetic techniques, such as array Comparative Genomic Hybridization. The detection of cryptic microdeletion/microduplication abnormalities has allowed genotype-phenotype correlations, delineating recognizable syndromic conditions that are herein reviewed. With the aim to provide to Paediatricians a combined clinical and genetic approach to the child with cognitive impairment, a practical diagnostic algorithm is also illustrated. The use of microarray platforms has further reduced the percentage of "idiopathic" forms of mental retardation, previously accounted for about half of total cases. We discussed the putative pathways at the basis of remaining "pure idiopathic" forms of mental retardation, highlighting possible environmental and epigenetic mechanisms as causes of altered cognition.