22q11.2 duplication and congenital heart defects

22q11.2 duplications: Expanding the clinical presentation

22q11.2 duplication syndrome has a frequency of ~1/700 in the intellectual disability population. Despite this frequency, there is limited information on the variable clinical presentation. Although the phenotype and incidence of congenital anomalies are well described for 22q11.2 deletion syndrome, they are not as well understood for individuals with 22q11.2 duplication syndrome. This study is a single-center, retrospective review of patients diagnosed with 22q11.2 duplication syndrome designed to categorize the variable phenotype seen in these individuals. The data suggest that the incidence of congenital anomalies may be higher than previously reported for this syndrome. Affected individuals are at increased risk for a variety of problems including gastrointestinal complications, endocrine dysfunction, ophthalmologic abnormalities, palatal anomalies, congenital heart disease, musculoskeletal differences, and neurologic abnormalities. Individuals with 22q11.2 duplication syndrome would benefit from care coordinated by a multidisciplinary team and managed according to the 22q11.2 deletion syndrome guidelines.

Chromosomal microarray analysis in prenatal diagnosis: ethical considerations of the Belgian approach

Detection of genetic aberrations in prenatal samples, obtained through amniocentesis or chorion villus biopsy, is increasingly performed using chromosomal microarray (CMA), a technique that can uncover both aneuploidies and copy number variants throughout the genome. Despite the obvious benefits of CMA, the decision on implementing the technology is complicated by ethical issues concerning variant interpretation and reporting. In Belgium, uniform guidelines were composed and a shared database for prenatal CMA findings was established. This Belgian approach sparks discussion: it is evidence-based, prevents inconsistencies and avoids parental anxiety, but can be considered paternalistic. Here, we reflect on the cultural and moral bases of the Belgian reporting system of prenatally detected variants.

Acute Pre-B Lymphoblastic Leukemia and Congenital Anomalies in a Child with a de Novo 22q11.1q11.22 Duplication

Microdeletions and microduplications are recurrent in the q11.2 region of chromosome 22. The 22q11.2 duplication syndrome is an extremely variable disorder with a phenotype ranging from severe intellectual disability, facial dysmorphism, heart defects, and urogenital abnormalities to very mild symptoms. Both benign and malignant hematological entities are rare. A male patient was diagnosed with mild facial dysmorphia, congenital heart anomalies shortly after birth and acute bowel obstruction due to malrotation of the intestine at the age of 3 years. A whole-genome single nucleotide polymorphism (SNP) array revealed a de novo 6.6 Mb duplication in the 22q11.1q11.22 chromosomal region. A year later, the patient was diagnosed with acute pre-B lymphoblastic leukemia (pre-B ALL). Five genes, CDC45, CLTCL1, DGCR2, GP1BB and SEPT5, in the 22q11.1q11.22 region are potentially responsible for cell cycle division. We hypothesized that dosage imbalance of genes implicated in the rearrangement could have disrupted the balance between cell growth and differentiation and played a role in the initiation of malignancy with a hyperdiploid leukemic clone, whereas over-expression of the TBX1 gene might have been responsible for congenital heart defects and mild facial dysmorphia.

The Belgian MicroArray Prenatal (BEMAPRE) database: A systematic nationwide repository of fetal genomic aberrations

OBJECTIVE

With the replacement of karyotyping by chromosomal microarray (CMA) in invasive prenatal diagnosis, new challenges have arisen. By building a national database, we standardize the classification and reporting of prenatally detected copy number variants (CNVs) across Belgian genetic centers. This database, which will link genetic and ultrasound findings with postnatal development, forms a unique resource to investigate the pathogenicity of variants of uncertain significance and to refine the phenotypic spectrum of pathogenic and susceptibility CNVs.

METHODS

The Belgian MicroArray Prenatal (BEMAPRE) consortium is a collaboration of all genetic centers in Belgium. We collected data from all invasive prenatal procedures performed between May 2013 and July 2016.

RESULTS

In this three-year period, 13 266 prenatal CMAs were performed. By national agreement, a limited number of susceptibility CNVs and no variants of uncertain significance were reported. Added values for using CMA versus conventional karyotyping were 1.8% in the general invasive population and 2.7% in cases with an ultrasound anomaly. Of the reported CNVs, 31.5% would have remained undetected with non-invasive prenatal test as the first-tier test.

CONCLUSION

The establishment of a national database for prenatal CNV data allows for a uniform reporting policy and the investigation of the prenatal and postnatal genotype-phenotype correlation.

Ocular findings associated with chromosome 22q11.2 duplication

We describe the ocular features of the chromosome 22q11.2 duplication syndrome and provide ophthalmologic examination recommendations for affected patients. The medical records of 19 children with chromosome 22q11.2 duplication who had undergone complete ophthalmological examination, including dilated fundus examination and cycloplegic refraction, were studied retrospectively. Over half of the children with 22q11.2 duplication syndrome were found to have visually significant ocular abnormalities, including 6 with strabismus, 2 with moderately high astigmatism requiring glasses, 1 with unilateral congenital cataract requiring surgery, 1 with optic disk drusen, 1 with bilateral megalocornea with normal eye pressures, 1 with nystagmus that resolved spontaneously, and 1 with delayed visual maturation. Because of the high incidence of conditions that could affect visual development, we recommend that children with 22q11.2 duplication syndrome have a complete ophthalmological examination on diagnosis and regular vision screenings by their primary care physician thereafter.

SNP Microarray in FISH Negative Clinically Suspected 22q11.2 Microdeletion Syndrome

The present study evaluated the role of SNP microarray in 101 cases of clinically suspected FISH negative (noninformative/normal) 22q11.2 microdeletion syndrome. SNP microarray was carried out using 300 K HumanCytoSNP-12 BeadChip array or CytoScan 750 K array. SNP microarray identified 8 cases of 22q11.2 microdeletions and/or microduplications in addition to cases of chromosomal abnormalities and other pathogenic/likely pathogenic CNVs. Clinically suspected specific deletions (22q11.2) were detectable in approximately 8% of cases by SNP microarray, mostly from FISH noninformative cases. This study also identified several LOH/AOH loci with known and well-defined UPD (uniparental disomy) disorders. In conclusion, this study suggests more strict clinical criteria for FISH analysis. However, if clinical criteria are few or doubtful, in particular newborn/neonate in intensive care, SNP microarray should be the first screening test to be ordered. FISH is ideal test for detecting mosaicism, screening family members, and prenatal diagnosis in proven families.

Congenital Heart Disease as a Warning Sign for the Diagnosis of the 22q11.2 Deletion

Background

To alert for the diagnosis of the 22q11.2 deletion syndrome (22q11.2DS) in patients with congenital heart disease (CHD).

Objective

To describe the main CHDs, as well as phenotypic, metabolic and immunological findings in a series of 60 patients diagnosed with 22q11.2DS.

Methods

The study included 60 patients with 22q11.2DS evaluated between 2007 and 2013 (M:F=1.3, age range 14 days to 20 years and 3 months) at a pediatric reference center for primary immunodeficiencies. The diagnosis was established by detection of the 22q11.2 microdeletion using FISH (n = 18) and/or MLPA (n = 42), in association with clinical and laboratory information. Associated CHDs, progression of phenotypic facial features, hypocalcemia and immunological changes were analyzed.

Results

CHDs were detected in 77% of the patients and the most frequent type was tetralogy of Fallot (38.3%). Surgical correction of CHD was performed in 34 patients. Craniofacial dysmorphisms were detected in 41 patients: elongated face (60%) and/or elongated nose (53.3%), narrow palpebral fissure (50%), dysplastic, overfolded ears (48.3%), thin lips (41.6%), elongated fingers (38.3%) and short stature (36.6%). Hypocalcemia was detected in 64.2% and decreased parathyroid hormone (PTH) level in 25.9%. Decrease in total lymphocytes, CD4 and CD8 counts were present in 40%, 53.3% and 33.3%, respectively. Hypogammaglobulinemia was detected in one patient and decreased concentrations of immunoglobulin M (IgM) in two other patients.

Conclusion

Suspicion for 22q11.2DS should be raised in all patients with CHD associated with hypocalcemia and/or facial dysmorphisms, considering that many of these changes may evolve with age. The 22q11.2 microdeletion should be confirmed by molecular testing in all patients.

Chromosome 22q11.2 duplication is rare in a population-based cohort of Danish children with cardiovascular malformations

The prevalence of the 22q11.2 duplication is unknown in children with cardiovascular malformations (CVMs). As most individuals with the duplication are detected in the search for other conditions, especially the 22q11.2 deletion, CVMs associated with the duplication are subject to referral bias. We circumvented this bias by investigating the prevalence of the 22q11.2 duplication in a population-based cohort of children with CVMs. The study population was defined as children born in 2000-2008, who were registered in the Danish National Patient Registry with a diagnosis of CVM from one of the two national university departments of pediatric cardiology. Sensitive multiplex ligation-dependent probe amplification was performed on dried blood spot samples from each individual's neonatal screening test. The study population consisted of 2,952 children with CVMs, 2,424 of whom were eligible for genetic testing; 13 individuals (0.5% [0.3-0.9%]) carried the duplication. Nine individuals (69%) had not previously been tested for a copy number variation on chromosome 22q11.2 in the clinical setting for children with CVMs. We conclude that 22q11.2 duplication is rare in children with CVMs, and is primarily found in malformations that are also associated with the 22q11.2 deletion.