Diagnostic Approach to Microdeletion Syndromes Based on 22q11.2 Investigation: Challenges in Four Cases

Access to genetic evaluation of 1463 individuals with orofacial cleft in Brazil

OBJECTIVE

The current study delves into the accessibility of genetic evaluations for individuals with orofacial clefts (OC), comparing data between genetics and treatment centers across Brazil.

METHODS

This cross-sectional retrospective study analyzed primary data from 1463 OC individuals registered in the Brazilian Database of Craniofacial Anomalies (BDCA) between 2008 and 2018 without age or sex selection. Diagnostic exam results stemming from research projects until 2023 were considered.

RESULTS

Of the 1463 individuals with typical OC, 987 were non-syndromic, 462 were syndromic (SOC), 10 presented atypical forms, and three were not specified OC cases. The average age for accessing laboratory diagnosis was 8.5 years among SOC individuals. Notably, more SOC cases were registered in genetics centers than treatment and rehabilitation centers (37.1 % vs. 29 %, p = 0.0015). Those originating from genetics centers accessed diagnosis at an average age of 7.3 years, while those from treatment and rehabilitation centers experienced delays with an average age of 10.7 years (p = 0.0581).

CONCLUSIONS

Irrespective of the center of origin, the data highlight delayed diagnosis and challenges in accessing genetic tests for the syndromic group. Given the widespread reliance on the public health system by most of the Brazilian population, disseminating this data can significantly contribute to shaping an informed perspective on healthcare access. These insights can improve public policies tailored to the unique needs of individuals with OC.

From karyotypes to precision genomics in 9p deletion and duplication syndromes

While 9p deletion and duplication syndromes have been studied for several years, small sample sizes and minimal high-resolution data have limited a comprehensive delineation of genotypic and phenotypic characteristics. In this study, we examined genetic data from 719 individuals in the worldwide 9p Network Cohort: a cohort seven to nine times larger than any previous study of 9p. Most breakpoints occur in bands 9p22 and 9p24, accounting for 35% and 38% of all breakpoints, respectively. Bands 9p11 and 9p12 have the fewest breakpoints, with each accounting for 0.6% of all breakpoints. The most common phenotype in 9p deletion and duplication syndromes is developmental delay, and we identified eight known neurodevelopmental disorder genes in 9p22 and 9p24. Since it has been previously reported that some individuals have a secondary structural variant related to the 9p variant, we examined our cohort for these variants and found 97 events. The top secondary variant involved 9q in 14 individuals (1.9%), including ring chromosomes and inversions. We identified a gender bias with significant enrichment for females (p = 0.0006) that may arise from a sex reversal in some individuals with 9p deletions. Genes on 9p were characterized regarding function, constraint metrics, and protein-protein interactions, resulting in a prioritized set of genes for further study. Finally, we achieved precision genomics in one child with a complex 9p structural variation using modern genomic technologies, demonstrating that long-read sequencing will be integral for some cases. Our study is the largest ever on 9p-related syndromes and provides key insights into genetic factors involved in these syndromes.

Brazil's Craniofacial Project: Different approaches on orofacial clefts and 22q11.2 deletion syndrome

This article reports the present situation of Brazilian health care in genetics for Orofacial Cleft (OFC) and 22q11.2 Deletions Syndrome (22q11.2 DS) based on research conducted by Brazil's Craniofacial Project (BCFP). Established in 2003, BCFP is a voluntary and cooperative network aiming to investigate the health care of people with these diseases and other craniofacial anomalies. The initiatives and research results are presented in four sections: (a) a comprehensive report of the Brazilian public health system in craniofacial genetics; (b) multicentric studies developed on OFC and 22q11.2 DS; (c) education strategies focused on addressing these conditions for both population and health-care professionals; and (d) the nosology through the Brazilian Database on Craniofacial Anomalies (BDCA). Since 2006, BDCA uses a standardized method with detailed clinical data collection, which allows for conducting studies on nosology, genotype-phenotype correlations, and natural history; data can also contribute to public policies. Currently, the BDCA stores data on 1,724 individuals, including 1,351 (78.36%) who were primarily admitted due to OFC and 373 (21.63%) with clinical suspicion of 22q11.2 DS. Chromosomal abnormalities/genomic imbalances were represented by 92/213 (43.19%) individuals with syndromic OFC, including 43 with 22q11.2 DS, which indicates the need for chromosomal microarray analysis in this group. The nosologic diversity reinforces that monitoring clinical is the best strategy for etiological investigation. BCFP's methodology has introduced the possibility of increasing scientific knowledge and genetic diagnosis of OFC and 22q11.2 DS to in turn improve health care and policies for this group of diseases.

Impact of Cranial Base Abnormalities on Cerebellar Volume and the Velopharynx in 22q11.2 Deletion Syndrome

OBJECTIVE

The purpose of this study was to analyze the relationship between cranial base, cerebellar, craniofacial, and velopharyngeal (VP) variables in individuals with 22q11.2 deletion syndrome (22q11DS).

METHODS

Thirteen typically developing healthy children and 13 age- and sex-matched individuals with 22q11DS completed a magnetic resonance imaging scan, which was used to examine craniofacial and VP variables.

RESULTS

A statistically significant difference was noted in cerebellum volumes, F_1,24 = 7.947, P = .010, posterior nasal spine to posterior pharyngeal wall (PNS-PPW), F_1,24 = 4.878, P = .037, nasion-sella-basion (NSB) cranial base angles, F_1,24 = 7.253, P = .013, and sella-basion-opisthion (SBO) cranial base angles, F_1,24 = 9.134, P = .006, between children with 22q11DS and controls. The cerebellum volume was significantly reduced and cranial base angles were significantly more obtuse in individuals with 22q11DS. In the 22q11DS group, cerebellum volume was significantly correlated with sella-basion (SB) length, osseous pharyngeal depth, the PNS-PPW length, and velar length (P < .05). The PNS-PPW length was correlated with SB length, basion-opisthion length, NSB angle, SBO angle, and the VP ratio (P < .05).

CONCLUSION

This study supports previous findings on anatomical differences among individuals with 22q11DS and has expanded our current understanding of the potential relationship between craniofacial and VP variables in at least a subset of children with 22q11DS. Results provide preliminary insights into the potential relationship between a decrease in cerebellar volume, obtuse cranial base angles, and unfavorable VP dimensions.

The 22q11.2 Microdeletion in Pediatric Patients with Cleft Lip, Palate, or Both and Congenital Heart Disease: A Systematic Review

The 22q11.2 deletion syndrome (22q11.2DS) is present in approximately 5 to 8% of patients with cleft lip, palate, or both (CL/P) and 75 to 80% of patients with congenital heart disease (CHD). In a literature review, we consider this association of 22q11.2DS in pediatric patients with CL/P and CHD. Early diagnosis of 22q11.2DS in pediatric patients with CL/P and CHD helps to optimize a multidisciplinary treatment approach for 22q11DS. Early diagnosis, thereby, can improve quality of life for these patients and awareness of other potential clinical implications that may require attention throughout the patient's life.

Phenotype comparison among individuals with developmental delay/intellectual disability with or without genomic imbalances

BACKGROUND

The chromosomal microarray analysis (CMA) is recommended as a first-tier test for individuals with developmental delay (DD)/intellectual disability (ID) and/or multiple congenital anomalies. However, owing to high costs, this technique is not widely performed for diagnostic purposes in several countries. The aim of this study was to identify clinical features that could favour the hypothesis of genomic imbalances (GIs) in individuals with DD/ID.

METHODS

The sample consisted of 63 individuals, and all of them underwent a detailed evaluation by a clinical geneticist and were investigated by the CMA. They were divided into two groups. Group A composed of 20 individuals with pathogenic copy number variants (CNVs); and group B composed of 43 individuals with normal CMA results or variants of uncertain clinical significance (VUS).

RESULTS

Pathogenic GIs were found in 20 cases (32%), including 11 individuals with an abnormal karyotype, VUS was found in five individuals (8%) and the results were normal in 38 individuals (60%). Major anomalies were found in 15/20 (75%) individuals in group A against 35/43 (81%) in group B. Dysmorphisms (≥5) were found in 17/20 (85%) in group A and 41/43 (95%) in group B. The most frequent major anomalies detected in group A were congenital heart disease, epilepsy and renal malformation; and in group B, they were malformations of central nervous system, congenital heart disease, microcephaly, epilepsy and hearing impairment. There was no significant statistical difference among the frequencies in groups A and B.

CONCLUSIONS

Evidences point that every individual with DD/ID, with no specific clinical suspicion, should have screening for GIs as a first-tier test, regardless of the presence or absence of additional major anomalies or dysmorphisms. Future studies with a similar design would be helpful, especially in countries where the access to new technologies is still limited.