High-Resolution genomic arrays identify CNVs that phenocopy the chromosome 22q11.2 deletion syndrome

Hypoparathyroidism Associated with Benign Thyroid Nodules in DiGeorge-like Syndrome: A Rare Case Report and Literature Review

BACKGROUND

DiGeorge-like syndrome (DGLS) is a rare genetic disorder due to the presence of the same classical clinical manifestations of DiGeorge syndrome (DGS) without its typical deletion. In the DGLS phenotype, hypoparathyroidism seldom occurs and is considered rare. In DGS, hypocalcemia affects up to 70% of patients, and a considerable share often has asymptomatic thyroid abnormalities.

CASE PRESENTATION

In this study, we describe an unusual case of a 16-year-old patient with DGLS due to a duplication of 365 kb in the 20p11.22 region, affected by hypoparathyroidism associated with thyroid nodule. The intraoperative parathyroid evaluation ruled out agenesis as a cause of hypoparathyroidism. In addition, we carried out a thorough literature review from 2010 to 2023 of DGLS cases using specific keywords, such as "22q11.2 deletion syndrome", "Di- George-like Syndrome", "hypoparathyroidism", "thyroid", and "children", analyzing 119 patients with DGLS.

CONCLUSION

Interestingly enough, the present case represents, to our knowledge, the first report of a patient with DGLS associated with hypoparathyroidism and the presence of thyroid nodules where an intraoperative observation reported a non-functional parathyroid gland.

Updated clinical practice recommendations for managing children with 22q11.2 deletion syndrome

This review aimed to update the clinical practice guidelines for managing children and adolescents with 22q11.2 deletion syndrome (22q11.2DS). The 22q11.2 Society, the international scientific organization studying chromosome 22q11.2 differences and related conditions, recruited expert clinicians worldwide to revise the original 2011 pediatric clinical practice guidelines in a stepwise process: (1) a systematic literature search (1992-2021), (2) study selection and data extraction by clinical experts from 9 different countries, covering 24 subspecialties, and (3) creation of a draft consensus document based on the literature and expert opinion, which was further shaped by survey results from family support organizations regarding perceived needs. Of 2441 22q11.2DS-relevant publications initially identified, 2344 received full-text reviews, including 1545 meeting criteria for potential relevance to clinical care of children and adolescents. Informed by the available literature, recommendations were formulated. Given evidence base limitations, multidisciplinary recommendations represent consensus statements of good practice for this evolving field. These recommendations provide contemporary guidance for evaluation, surveillance, and management of the many 22q11.2DS-associated physical, cognitive, behavioral, and psychiatric morbidities while addressing important genetic counseling and psychosocial issues.

Updated clinical practice recommendations for managing adults with 22q11.2 deletion syndrome

This review aimed to update the clinical practice guidelines for managing adults with 22q11.2 deletion syndrome (22q11.2DS). The 22q11.2 Society recruited expert clinicians worldwide to revise the original clinical practice guidelines for adults in a stepwise process according to best practices: (1) a systematic literature search (1992-2021), (2) study selection and synthesis by clinical experts from 8 countries, covering 24 subspecialties, and (3) formulation of consensus recommendations based on the literature and further shaped by patient advocate survey results. Of 2441 22q11.2DS-relevant publications initially identified, 2344 received full-text review, with 2318 meeting inclusion criteria (clinical care relevance to 22q11.2DS) including 894 with potential relevance to adults. The evidence base remains limited. Thus multidisciplinary recommendations represent statements of current best practice for this evolving field, informed by the available literature. These recommendations provide guidance for the recognition, evaluation, surveillance, and management of the many emerging and chronic 22q11.2DS-associated multisystem morbidities relevant to adults. The recommendations also address key genetic counseling and psychosocial considerations for the increasing numbers of adults with this complex condition.

Proximal variants in CCND2 associated with microcephaly, short stature, and developmental delay: A case series and review of inverse brain growth phenotypes

Cyclin D2 (CCND2) is a critical cell cycle regulator and key member of the cyclin D2-CDK4 (DC) complex. De novo variants of CCND2 clustering in the distal part of the protein have been identified as pathogenic causes of brain overgrowth (megalencephaly, MEG) and severe cortical malformations in children including the megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndrome. Megalencephaly-associated CCND2 variants are localized to the terminal exon and result in accumulation of degradation-resistant protein. We identified five individuals from three unrelated families with novel variants in the proximal region of CCND2 associated with microcephaly, mildly simplified cortical gyral pattern, symmetric short stature, and mild developmental delay. Identified variants include de novo frameshift variants and a dominantly inherited stop-gain variant segregating with the phenotype. This is the first reported association between proximal CCND2 variants and microcephaly, to our knowledge. This series expands the phenotypic spectrum of CCND2-related disorders and suggests that distinct classes of CCND2 variants are associated with reciprocal effects on human brain growth (microcephaly and megalencephaly due to possible loss or gain of protein function, respectively), adding to the growing paradigm of inverse phenotypes due to dysregulation of key brain growth genes.

Screening of 22q11.2DS Using Multiplex Ligation-Dependent Probe Amplification as an Alternative Diagnostic Method

Background

The 22q11.2 deletion syndrome (22q11.2DS) is the most common form of deletion disorder in humans. Low copy repeats flanking the 22q11.2 region confers a substrate for nonallelic homologous recombination (NAHR) events leading to rearrangements which have been reported to be associated with highly variable and expansive phenotypes. The 22q11.2DS is reported as the most common genetic cause of congenital heart defects (CHDs).

Methods

A total of 42 patients with congenital heart defects, as confirmed by echocardiography, were recruited. Genetic molecular analysis using a fluorescence in situ hybridization (FISH) technique was conducted as part of routine 22q11.2DS screening, followed by multiplex ligation-dependent probe amplification (MLPA), which serves as a confirmatory test.

Results

Two of the 42 CHD cases (4.76%) indicated the presence of 22q11.2DS, and interestingly, both cases have conotruncal heart defects. In terms of concordance of techniques used, MLPA is superior since it can detect deletions within the 22q11.2 locus and outside of the typically deleted region (TDR) as well as duplications.

Conclusion

The incidence of 22q11.2DS among patients with CHD in the east coast of Malaysia is 0.047. MLPA is a scalable and affordable alternative molecular diagnostic method in the screening of 22q11.2DS and can be routinely applied for the diagnosis of deletion syndromes.

Elucidating the diagnostic odyssey of 22q11.2 deletion syndrome

Clinical molecular testing has been available for 22q11.2 deletion syndrome (22q11.2DS) for over two decades yet under-recognition and diagnostic delays are common. To characterize the "diagnostic odyssey" in 22q11.2DS we studied 202 well-characterized unrelated adults, none ascertained through an affected relative. We used a regression model to identify clinical and demographic factors associated with length of time to molecular diagnosis. Kaplan-Meier analysis compared time to diagnosis for the molecular testing era (since 1994) and earlier birth cohorts. The results showed that the median time to molecular diagnosis of the 22q11.2 deletion was 4.7 (range 0-20.7) years. Palatal and cardiac anomalies, but not developmental delay/intellectual disability, were associated with a shorter time to molecular diagnosis. Non-European ethnicity was associated with longer time to diagnosis. Inclusion of a cohort from another 22q11.2DS center increased power to observe a significantly earlier diagnosis for patients born in the molecular testing era. Nonetheless, only a minority were diagnosed in the first year of life. On average, patients were seen in seven (range 2-15) different clinical specialty areas prior to molecular diagnosis. The findings indicate that even for those born in the molecular testing era, individuals with 22q11.2DS and their families face a diagnostic odyssey that is often prolonged, particularly in the absence of typical physical congenital features or for those of non-European ancestry. The results support educational efforts to improve clinical recognition and testing, and ultimately newborn screening as a means of maximizing early detection that would provide the best opportunity to optimize outcomes.

Genomic imbalances in syndromic congenital heart disease

OBJECTIVE

To identify pathogenic genomic imbalances in patients presenting congenital heart disease (CHD) with extra cardiac anomalies and exclusion of 22q11.2 deletion syndrome (22q11.2 DS).

METHODS

78 patients negative for the 22q11.2 deletion, previously screened by fluorescence in situ hybridization (FISH) and/or multiplex ligation probe amplification (MLPA) were tested by chromosomal microarray analysis (CMA).

RESULTS

Clinically significant copy number variations (CNVs ≥300kb) were identified in 10% (8/78) of cases. In addition, potentially relevant CNVs were detected in two cases (993kb duplication in 15q21.1 and 706kb duplication in 2p22.3). Genes inside the CNV regions found in this study, such as IRX4, BMPR1A, SORBS2, ID2, ROCK2, E2F6, GATA4, SOX7, SEMAD6D, FBN1, and LTPB1 are known to participate in cardiac development and could be candidate genes for CHD.

CONCLUSION

These data showed that patients presenting CHD with extra cardiac anomalies and exclusion of 22q11.2 DS should be investigated by CMA. The present study emphasizes the possible role of CNVs in CHD.

DiGeorge-like syndrome in a child with a 3p12.3 deletion involving MIR4273 gene born to a mother with gestational diabetes mellitus

Chromosome 22q11.2 deletion is the most common chromosomal alteration associated with DiGeorge syndrome (DGS), even though this is not the only underlying cause of DGS. In rare patients, mutations in a single gene, TBX1, have been described resulting in a DGS phenotype. Recently, it has been reported that at least part of the TBX1 mutant phenotype is due to excessive bone morphogenetic proteins (BMP) signaling. Evidence suggests that miRNA may modulate the expression of critical T-box transcriptional regulators during midface development and Bmp-signaling. We report on a 7-year-old Caucasian male born to a mother affected with gestational diabetes (GDM) who had a 371Kb-interstitial deletion of 3p12.3 identified by array CGH, involving the ZNF717, MIR1243, and 4273 genes. The child presented with a DiGeorge anomaly (DGA) associated with unilateral renal agenesis and language delay. The immunological evaluation revealed a severe reduction and impairment of T lymphocytes. FISH analysis and TBX1 sequencing were negative. Among the miRNA-4273 predicted target genes, we found BMP3, which is involved in several steps of embryogenesis including kidney and lung organogenesis and in insulin gene expression. Since, DGA is not commonly found in newborns of diabetic mothers, we hypothesize that the pathogenesis of DGA associated with GDM is multifactorial, involving both genetic and/or epigenetic cofactors.

8p23.1 Interstitial Deletion in a Patient with Congenital Cardiopathy, Neurobehavioral Disorders, and Minor Signs Suggesting 22q11.2 Deletion Syndrome

Copy number variation studies of known disorders have the potential to improve the characterization of clinical phenotypes and may help identifying candidate genes and their pathways. The authors described a child with congenital heart disease, microcephaly, facial dysmorphisms, developmental delay, learning difficulties, and behavioral problems. There was initially a clinical suspicion of 22q11.2 deletion syndrome (22q11.2 DS), but molecular cytogenetic analysis (array genomic hybridization [aGH]) showed the presence of a de novo 3.6-Mb interstitial microdeletion in 8p23.1. The main features of 8p23.1 DS include congenital heart disease and behavioral problems, in addition to minor dysmorphisms and mental delay. Therefore, this article highlights the application of aGH to investigate 8p23.1 deletion in nonconfirmed 22q11.2 DS patients presenting neurobehavioral disorders, congenital cardiopathy, and minor dysmorphisms.

Connecting teratogen-induced congenital heart defects to neural crest cells and their effect on cardiac function

Neural crest cells play many key roles in embryonic development, as demonstrated by the abnormalities that result from their specific absence or dysfunction. Unfortunately, these key cells are particularly sensitive to abnormalities in various intrinsic and extrinsic factors, such as genetic deletions or ethanol-exposure that lead to morbidity and mortality for organisms. This review discusses the role identified for a segment of neural crest in regulating the morphogenesis of the heart and associated great vessels. The paradox is that their derivatives constitute a small proportion of cells to the cardiovascular system. Findings supporting that these cells impact early cardiac function raises the interesting possibility that they indirectly control cardiovascular development at least partially through regulating function. Making connections between insults to the neural crest, cardiac function, and morphogenesis is more approachable with technological advances. Expanding our understanding of early functional consequences could be useful in improving diagnosis and testing therapies.

A boy with mild mental retardation, mild sensorineural hearing loss and mild facial dysmorphism caused by a 19p13.2 deletion: a case report and review of the literature

The investigation of patients with congenital anomalies and/or intellectual disability with modern genetic methods allows the recognition of an increasing number of cases with these chromosomal rearrangements. Here, we present a mildly mentally retarded boy with mild facial dysmorphism, language development delay, mild sensorineural hearing loss due to a deletion of 1,14 Mb on chromosome 19p 13.2. The deletion was de novo and familial history negative for this disorder. To our knowledge this is the first description of a patient with symptoms mentioned above associated with a 19p13.2-p13.2 deletion.

Further Evidence of Contrasting Phenotypes Caused by Reciprocal Deletions and Duplications: Duplication of NSD1 Causes Growth Retardation and Microcephaly

Microduplications of the Sotos syndrome region containing NSD1 on 5q35 have recently been proposed to cause a syndrome of microcephaly, short stature and developmental delay. To further characterize this emerging syndrome, we report the clinical details of 12 individuals from 8 families found to have interstitial duplications involving NSD1, ranging in size from 370 kb to 3.7 Mb. All individuals are microcephalic, and height and childhood weight range from below average to severely restricted. Mild-to-moderate learning disabilities and/or developmental delay are present in all individuals, including carrier family members of probands; dysmorphic features and digital anomalies are present in a majority. Craniosynostosis is present in the individual with the largest duplication, though the duplication does not include MSX2, mutations of which can cause craniosynostosis, on 5q35.2. A comparison of the smallest duplication in our cohort that includes the entire NSD1 gene to the individual with the largest duplication that only partially overlaps NSD1 suggests that whole-gene duplication of NSD1 in and of itself may be sufficient to cause the abnormal growth parameters seen in these patients. NSD1 duplications may therefore be added to a growing list of copy number variations for which deletion and duplication of specific genes have contrasting effects on body development.

Genotype-phenotype correlation in 22q11.2 deletion syndrome

BACKGROUND

The 22q11.2 deletion syndrome (22q11.2DS) is caused by hemizygous microdeletions on chromosome 22q11.2 with highly variable physical and neuropsychiatric manifestations. We explored the genotype-phenotype relationship in a relatively large 22q11.2DS cohort treated and monitored in our clinic using comprehensive clinical evaluation and detailed molecular characterization of the deletion.

METHODS

Molecular analyses in 142 subjects with 22q11.2DS features were performed by FISH and MLPA methods. Participants underwent clinical assessment of physical symptoms and structured psychiatric and cognitive evaluation.

RESULTS

Deletions were found in 110 individuals including one with an atypical nested distal deletion which was missed by the FISH test. Most subjects (88.2%) carried the 3Mb typically deleted region and 11.8% carried 4 types of deletions differing in size and location. No statistically significant genotype-phenotype correlations were found between deletion type and clinical data although some differences in hypocalcemia and cardiovascular anomalies were noted.Analysis of the patient with the distal nested deletion suggested a redundancy of genes causing the physical and neuropsychiatric phenotype in 22q11.2DS and indicating that the psychiatric and cognitive trajectories may be governed by different genes.

CONCLUSIONS

MLPA is a useful and affordable molecular method combining accurate diagnosis and detailed deletion characterization. Variations in deletion type and clinical manifestations impede the detection of significant differences in samples of moderate size, but analysis of individuals with unique deletions may provide insight into the underlying biological mechanisms.Future genotype-phenotype studies should involve large multicenter collaborations employing uniform clinical standards and high-resolution molecular methods.

Microdeletion 19p13.2 in an almost 5-year-old boy

Deletions of the short arm of chromosome 19 are rarely found by conventional cytogenetic techniques. This region has a high gene density and this is likely the reason why deletions in this region are associated with a severe phenotype. Since the implementation of modern high-resolution SNP- and CGH-array techniques more cases have been reported. Here, we present an almost 5-year-old boy with intellectual disability, minor dysmorphisms, febrile seizures, and a de novo deletion of 834.2 kb on 19p13.2 encompassing 32 genes. The deletion was found by the Illumina Infinium HD Human1M-Duo v1 BeadChip SNP-array and confirmed by the NimbleGen Human CGH 2.1M Whole Genome Tiling v2.0D oligonucleotide array. PCR amplification of the junction fragment and subsequent sequencing defined the breakpoints and indicated that formation was mediated by non-allelic homologous recombination (NAHR). The phenotype of our patient shows that microrearrangements even at gene-dense chromosomes may result in mild clinical consequences.