A review of 18p deletions

TYMS-ENOSF1 Dyskeratosis Congenita in a Patient With Ring Chromosome 18: A Case Report

Dyskeratosis Congenita (DC) is a rare genetic syndrome due to variants in genes involved in telomeric regulation and maintenance, impacting multiple organ systems. We report a case of DC secondary to TYMS gene deletion in a patient with ring chromosome 18 and related partial monosomy 18p and 18q. TYMS encodes thymidylate synthase, and compound heterozygosity for loss of function variants in TYMS and a specific haplotype of its antisense regulator ENOSFI (enolase super family 1) causes digenic DC. The patient had physical and developmental features of 18p monosomy, including poor growth, feeding issues, distinctive facial features, and strabismus. In early infancy, he developed diffuse hyperpigmentation as well as numerous punctate hypopigmented macules, sparse hair, and nail dystrophy, and diagnosis of DC was confirmed with a telomere length assay. Our case highlights that individuals with deletions at 18p encompassing TYMS should be evaluated for features of digenic dyskeratosis congenita.

Chromosome aberrations and autoimmunity: Immune-mediated diseases associated with 18p deletion and other chromosomal aberrations

Recent advances in genomic methodologies have significantly enhanced our understanding of immune-mediated rheumatic diseases. Specific structural variants (SVs), such as substantial DNA deletions or insertions, including chromosomal aberrations, have been implicated in diseases of immune dysregulation. Regrettably, SVs are frequently overlooked in next-generation sequencing (NGS) targeted-gene panels, whole exome sequencing (WES) and whole genome sequencing (WGS). In view of a case of chromosome 18p deletion syndrome, characterized by hypogammaglobulinemia and an autoinflammatory phenotype, we provide a comprehensive review on chromosome aberrations associated with multiple immune-mediated conditions, highlighting the clinical aspects of the various chromosome aberrations associated with immune-mediated diseases. Further investigations and development of functional tests should contribute to elucidate the mechanistic connection between chromosome aberrations and Primary Immune Regulatory Disorders (PIRD), bringing novel perspectives in the field of autoinflammatory and autoimmune diseases.

The behavioral phenotype in a cohort of patients with chromosome 18 anomalies: a retrospective observational study

BACKGROUND

Genetic syndromes resulting from chromosome 18 structural abnormalities constitute a broad spectrum of conditions characterized by significant clinical heterogeneity. Most studies in the literature focus on case reports and clinical observations; the present study aims to assess the cognitive, communicative, behavioral, and adaptive abilities of different chromosome 18 abnormalities. In addition, this work aims to identify phenotype-genotype correlations by comparing individuals with 18p deletion, 18q deletion, and 18p tetrasomy.

METHODS

The sample included 24 patients with a definite genetic diagnosis of 18p deletion (N = 6), 18q deletion (N = 9), or 18p tetrasomy (N = 8). The assessment is provided by using a specific protocol based on direct and indirect clinical assessment of patients. Differences in IQ/GQ indexes, adaptive behavior, CARS scores, and CBCL internalizing and externalizing symptoms were assessed using ANCOVAs with age as covariate.

RESULTS

Our results showed more significant cognitive and behavioral impairment in tetrasomy 18 than in the other two conditions. Conversely, in 18p deletion group, we found greater behaviorally susceptibility to develop autistic traits.

CONCLUSION

These preliminary findings should raise clinicians' awareness of the strengths and weaknesses of patients with chromosome 18 alterations, paving the way to targeted and more appropriate management.

Monosomy 18p with Unbalanced Translocation Between 13 and 18 Chromosomes: First Reported Case in Serbia

Background: Monosomy 18p is a chromosomal disorder resulting from the deletion of the short arm of chromosome 18. While a lot of cases result from the partial deletion of 18p, only a few reported cases are caused by the deletion of the whole short arm of chromosome 18 due to unbalanced translocations occurring between chromosomes 13 and 18 (13;18). 18p- monosomy presents with a variety of clinical manifestations, including facial dysmorphism, intellectual disability, and short stature, among others. Case presentation: Here, we report a case of a one-year-old girl with 18p- monosomy resulting from an unbalanced translocation between chromosomes 13 and 18 (45, XX, t(13;18) (q12:p11.2)). Our patient had facial dysmorphism and stunted growth. Additionally, she had hypotonia and required thyroxine supplementation from a young age. To our knowledge, this is the first case of astigmatism in a patient with this deletion and an unbalanced translocation between chromosomes 13 and 18. Conclusions: The present case demonstrates the phenotypic spectrum of a rare variant of monosomy 18 caused by an unbalanced whole-arm translocation between chromosomes 13 and 18. Our study emphasizes the significance of cytogenetic testing to diagnose this disease, which has been described only five times in the literature.

SMCHD1 genetic variants in type 2 facioscapulohumeral dystrophy and challenges in predicting pathogenicity and disease penetrance

The molecular diagnosis of type 1 facioscapulohumeral muscular dystrophy (FSHD1) relies on the detection of a shortened D4Z4 array at the 4q35 locus. Until recently, the diagnosis of FSHD2 relied solely on the absence of a shortened D4Z4 allele in clinically affected patients. It is now established that most FSHD2 cases carry a heterozygous variant in the SMCHD1 gene. A decrease in D4Z4 DNA methylation is observed in both FSHD1 and FSHD2 patients. To refine the molecular diagnosis of FSHD2, we performed a molecular diagnosis of SMCHD1 in 54 patients with a clinical diagnosis of FSHD. All patients carry a D4Z4 array of more than 10 D4Z4 units, or a cis-duplication of the locus. Forty-eight of them carry a variant in SMCHD1 and six other cases are hemizygous for the 18p32 locus encompassing SMCHD1. Genetic and epigenetic analyses were considered to assess the pathogenicity of new SMCHD1 variants and of variants previously classified as likely pathogenic. In comparison to the healthy population and FSHD1 patients, we defined a threshold of 40% of methylation at the D4Z4 DR1 site as associated with SMCHD1 variants or SMCHD1 hemizygosity. We also showed that the number of D4Z4 on the shortest 4q allele ranges from 11 up to 35 units in these same patients. Using variant interpretation and protein structure prediction tools, we also highlight the difficulty in interpreting the impact of pathogenic variants on SMCHD1 function. Our study further emphasizes the intriguing relationship between D4Z4 methylation, SMCHD1 variants with SMCHD1 protein structure-function in FSHD.

Understanding type and quality of relationships between individuals with chromosome 18 syndromes and their siblings

Siblings of individuals with disabilities hold a pivotal and sometimes unappreciated position in the lives of their brother or sister. We sought to understand the unique challenges and opportunities in relationships between children with chromosome 18 conditions and their siblings and to identify the ways to support this relationship. Participants were recruited through the lay advocacy organization, the Chromosome 18 Registry & Research Society. Fifty-seven siblings from 36 families participated, using an investigator designed instrument, were asked to agree or disagreed with statements from four content areas (information and knowledge about the syndrome, feelings about the sibling relationship, involvement with and caregiving for their sibling, and support and advocacy). Siblings reported that they know their sibling with a disability very well and reported a wide range of emotions regarding their sibling. There was a strong sense of pride in their brother/sister's abilities, and many participants reported attempts to help others understand their brother/sister. Many siblings reported a dislike for the common assumption that their affected sibling is a burden on the family. Most participants reported feeling some degree of responsibility for their affected sibling, but many also reported that they enjoy this role. Sixty-three parents from 36 families responded to the survey. Most parents felt their typically developing children enjoyed teaching new things to their affected child as well as being a good role model for them. Most parents also felt their typically developing child was comfortable telling others about their sibling's condition. Recommendations for interventions and future research are discussed.

Monozygotic triplets with juvenile-onset autoimmunity and 18p microdeletion involving PTPRM

Abnormal gene dosage from copy number variants has been associated with susceptibility to autoimmune disease. This includes 18p deletion syndrome, a chromosomal disorder with an estimated prevalence of 1 in 50,000 characterized by intellectual disability, facial dysmorphology, and brain abnormalities. The underlying causes for autoimmune manifestations associated with 18p deletions, however, remain unknown. Our objective was to investigate a distinctive case involving monozygotic triplets concordant for developmental delay, white matter abnormalities, and autoimmunity, specifically juvenile-onset Graves' thyroiditis. By chromosomal microarray analysis and whole genome sequencing, we found the triplets to carry a de novo interstitial 5.9 Mb deletion of chromosome 18p11.31p11.21 spanning 19 protein-coding genes. We conducted a literature review to pinpoint genes affected by the deletion that could be associated with immune dysregulation and identified PTPRM as a potential candidate. Through dephosphorylation, PTPRM serves as a negative regulator of STAT3, a key factor in the generation of Th17 cells and the onset of specific autoimmune manifestations. We hypothesized that PTPRM hemizygosity results in increased STAT3 activation. We therefore performed assays investigating PTPRM expression, STAT3 phosphorylation, Th1/Th2/Th17 cell fractions, Treg cells, and overall immunophenotype, and in support of the hypothesis, our investigations showed an increase in cells with phosphorylated STAT3 and higher levels of Th17 cells in the triplets. We propose that PTPRM hemizygosity can serve as a contributing factor to autoimmune susceptibility in 18p deletion syndrome. If confirmed in unrelated 18p/PTPRM deletion patients, this susceptibility could potentially be treated by targeted inhibition of IL-17.

Prenatal detection of distal 18p deletion by chromosomal microarray analysis: Three case reports and literature review

BACKGROUND

Chromosome 18p deletion syndrome is caused by total or partial deletion of the short arm of chromosome 18 and associated with cognitive impairment, growth retardation and mild facial dysmorphism. However, most studies on the genotype-phenotype correlations in the 18p region are diagnosed postnatally. Prenatal reports involving 18p deletions are limited.

METHODS

Three pregnant women opted for invasive prenatal testing due to noninvasive prenatal testing indicating high risk for chromosome 18 abnormalities. Karyotypic analysis and chromosomal microarray analysis (CMA) were performed simultaneously. The pregnancy outcomes for all cases were followed up. Meanwhile, we also made a literature review on prenatal phenotypes of 18p deletions.

RESULTS

G-banding analysis showed that 2 fetuses presented abnormal karyotypes: 45,XN,der(18)t(18;21)(p11; q11),-21 (case 2) and 46,XN,18p- (case 3). The karyotype of case 1 was normal. Meanwhile, CMA detected 4.37 Mb (case 1), 7.26 Mb (case 2) and 14.97 Mb (case 3) deletions in chromosome 18p region. All 3 pregnancies were terminated finally according to genetic counseling based upon abnormal CMA results.

CONCLUSION

Prenatal diagnosis of 18p deletion syndrome is full of challenges due to the phenotypic diversity, incomplete penetrance and lack of prenatal phenotypes. Increased nuchal translucency and holoprosencephaly are common prenatal phenotypes of distal 18p deletion. For fetuses carrying 18p deletions with atypical sonographic phenotypes, noninvasive prenatal testing could be adopted as an effective approach.

Prenatal diagnosis of dicentric chromosome X mosaicism: a case report and review

A dicentric chromosome is an abnormal chromosome with two centromeres on the same chromosome. It has been reported that dicentric chromosomes are specific biomarkers of radiation exposure, but dicentric chromosomes are rarely identified in newborns with multiple congenital anomalies. At 16 weeks of gestation, a 39-year-old pregnant woman (gravida 2, para 1) was referred to the prenatal diagnosis center for genetic counseling. The fetal ultrasonography indicated multiple anomalies. Subsequently, amniocentesis was performed, and the G-banding karyotype analysis showed a rare type of mosaicism. The C-banding karyotype analysis indicated a pseudo-dicentric chromosome X [psu dic (X; 18) (p11.2; p11.2)]. A single-nucleotide polymorphism array (SNP array) revealed three pathogenic copy number variations (CNVs). After genetic counseling, the parents chose to terminate this pregnancy. This study provides new evidence for a better understanding of the diagnosis of dicentric chromosomes and emphasizes on the importance of genetic counseling.

Cytogenomic characterization of small supernumerary marker chromosomes in patients with pigmentary mosaicism

Introduction

The combination of gene content on the marker chromosome, chromosomal origin, level of mosaicism, origin mechanism (chromothripsis), and uniparental disomy can influence the final characterization of sSMCs. Several chromosomal aberrations, including sSMCs, have been observed in 30%-60% of patients with pigmentary mosaicism, and in more than 80%, chromosomal abnormalities are present in the mosaic state. In patients with pigmentary mosaicism the most representative chromosomes involved in sSMCs are 3, 5, 6, 9, 10, 13, 15, 18, 20, and X. In this study, we included the complete clinical, cytogenetic, and molecular characterization of seven patients with pigmentary mosaicism associated with the presence of SMCs of different chromosomal origins.

Methods

The patients were diagnosed by the Genetics and Dermatology Department of three different hospitals. Cytogenetic and FISH analyses were performed on peripheral blood, light skin, and dark skin. FISH analysis was performed using different probes, depending on the marker chromosome description. Different array analysis was performed.

Results

To date, of the seven cases studied, the chromosomal origins of six were successfully identified by FISH or array analysis. The chromosomes involved in SMCs were 6, 9, 15, and 18, X. The most frequently found was the centric minute structure.

Discussion

To date, this group of seven patients constitutes the largest clinical and cytogenetically finely described study of cases with pigmentary mosaicism associated with sSMCs. Undoubtedly, analysis of the two skin types is a fundamental part of our study, as numerical differences may occur in the cell lines found in each skin type. The knowledge generated in this study will help delineate a very heterogeneous entity more accurately, and in the future, analyzing more patients with PM will likely establish a more definite association with the presence of this genetic alteration.

Prenatal diagnosis of 18p deletion and 8p trisomy syndrome: literature review and report of a novel case

18p deletion syndrome constitutes one of the most frequent autosomal terminal deletion syndromes, affecting one in 50,000 live births. The syndrome has un-specific clinical features which vary significantly between patients and may overlap with other genetic conditions. Its prenatal description is extremely rare as the fetal phenotype is often not present during pregnancy. Trisomy 8p Syndrome is characterized by heterogenous phenotype, with the most frequent components to be cardiac malformation, developmental and intellectual delay. Its prenatal diagnosis is very rare due to the unspecific sonographic features of the affected fetuses. We present a very rare case of a fetus with multiple anomalies diagnosed during the second trimester whose genomic analysis revealed a 18p Deletion and 8p trisomy Syndrome. This is the first case where this combination of DNA mutations has been described prenatally and the second case in general. The presentation of this case, as well as the detailed review of all described cases, aim to expand the existing knowledge regarding this rare condition facilitating its diagnosis in the future.

In skeletal muscle and neural crest cells, SMCHD1 regulates biological pathways relevant for Bosma syndrome and facioscapulohumeral dystrophy phenotype

Many genetic syndromes are linked to mutations in genes encoding factors that guide chromatin organization. Among them, several distinct rare genetic diseases are linked to mutations in SMCHD1 that encodes the structural maintenance of chromosomes flexible hinge domain containing 1 chromatin-associated factor. In humans, its function as well as the impact of its mutations remains poorly defined. To fill this gap, we determined the episignature associated with heterozygous SMCHD1 variants in primary cells and cell lineages derived from induced pluripotent stem cells for Bosma arhinia and microphthalmia syndrome (BAMS) and type 2 facioscapulohumeral dystrophy (FSHD2). In human tissues, SMCHD1 regulates the distribution of methylated CpGs, H3K27 trimethylation and CTCF at repressed chromatin but also at euchromatin. Based on the exploration of tissues affected either in FSHD or in BAMS, i.e. skeletal muscle fibers and neural crest stem cells, respectively, our results emphasize multiple functions for SMCHD1, in chromatin compaction, chromatin insulation and gene regulation with variable targets or phenotypical outcomes. We concluded that in rare genetic diseases, SMCHD1 variants impact gene expression in two ways: (i) by changing the chromatin context at a number of euchromatin loci or (ii) by directly regulating some loci encoding master transcription factors required for cell fate determination and tissue differentiation.

PRRT2 benign familial infantile seizures (BFIS) with atypical evolution to encephalopathy related to status epilepticus during sleep (ESES)

PURPOSE

Heterozygous variants in PRRT2 are mostly associated with benign phenotypes, being the major genetic cause of benign familial infantile seizures (BFIS), as well as in paroxysmal disorders. We report two children from unrelated families with BFIS that evolved to encephalopathy related to status epilepticus during sleep (ESES).

METHODS AND RESULTS

Two probands presented with focal motor seizures at 3 months of age, with a limited course. Both children presented, at around 5 years of age, with centro-temporal interictal epileptiform discharges with a source in the frontal operculum, markedly activated by sleep, and associated with stagnation on neuropsychological development. Whole-exome sequencing and co-segregation analysis revealed a frameshift mutation c.649dupC in the proline-rich transmembrane protein 2 (PRRT2) in both probands and all affected family members.

CONCLUSION

The mechanism leading to epilepsy and the phenotypic variability of PRRT2 variants remain poorly understood. However, its wide cortical and subcortical expression, in particular in the thalamus, could partially explain both the focal EEG pattern and the evolution to ESES. No variants in the PRRT2 gene have been previously reported in patients with ESES. Due to the rarity of this phenotype, other possible causative cofactors are likely contributing to the more severe course of BFIS in our probands.

A Neonatal Patient Diagnosed with Chromosome 18p 11.1 Microdeletion Syndrome Presented with Trisomy 18Like Phenotype

Microdeletion of the short arm of chromosome 18 is one of the most common chromosome deletion syndromes. Its estimated frequency is 1 in 50,000 live-born infants, with female prevalence over males. Around 150 cases have been described till now. The reported abnormalities include growth deficiency, hypotonia, microcephaly, dysmorphic facial features such as ptosis, epicanthal folds, hypertelorism and micrognathia, and relatively small hands and feet. Our patient was a full-term low birth weight (2150 gm) female newborn, showing cleft upper lip and palate (hard and soft palate), bilateral congenital Talipes Equinovarus with rocker bottom foot, microcephaly, atrial septal defect. She was initially conservatively managed with gavage feeding, then shifted into paladai feeding of expressed breast milk. A multidisciplinary approach was adopted due to various malformations and for the potential occurring complications. To our knowledge, this is the first case diagnosed during the neonatal period.

Neurodevelopmental copy-number variants: A roadmap to improving outcomes by uniting patient advocates, researchers, and clinicians for collective impact

Copy-number variants and structural variants (CNVs/SVs) drive many neurodevelopmental-related disorders. While many neurodevelopmental-related CNVs/SVs give rise to complex phenotypes, the overlap in phenotypic presentation between independent CNVs can be extensive and provides a motivation for shared approaches. This confluence at the level of clinical phenotype implies convergence in at least some aspects of the underlying genomic mechanisms. With this perspective, our Commission on Novel Technologies for Neurodevelopmental CNVs asserts that the time has arrived to approach neurodevelopmental-related CNVs/SVs as a class of disorders that can be identified, investigated, and treated on the basis of shared mechanisms and/or pathways (e.g., molecular, neurological, or developmental). To identify common etiologic mechanisms among uncommon neurodevelopmental-related disorders and to potentially identify common therapies, it is paramount for teams of scientists, clinicians, and patients to unite their efforts. We bring forward novel, collaborative, and integrative strategies to translational CNV/SV research that engages diverse stakeholders to help expedite therapeutic outcomes. We articulate a clear vision for piloted roadmap strategies to reduce patient/caregiver burden and redundancies, increase efficiency, avoid siloed data, and accelerate translational discovery across CNV/SV-based syndromes.

18p Deletion Syndrome Originating from Rare Unbalanced Whole-Arm Translocation between Chromosomes 13 and 18: A Case Report and Literature Review

18p deletion (18p-) syndrome is a rare chromosome abnormality that has a wide range of phenotypes, with short stature, intellectual disability, and facial dysmorphism being the main clinical features. Here, we report the first case in Korea of a 16-year-old male adolescent with 18p- syndrome resulting from de novo unbalanced whole-arm translocation between chromosomes 13 and 18 (45, XY, der(13;18)(q10:q10)). Three rare clinical findings were discovered that had not been reported in the previous literature; morbid obesity without other hormonal disturbances, rib cage deformity leading to the direct compression of the liver, and lumbar spondylolisthesis at the L5-S1 level. This case expands the phenotypic spectrum of 18p- syndrome and highlights the importance of considering chromosomal analysis, since this syndrome can be easily overlooked in a clinical setting, especially without distinctive symptoms of other organs, due to its nonspecific but typical features of short stature and mild intellectual disability with a mildly dysmorphic face. Moreover, since not all cases of 18p- syndrome with unbalanced translocation (13;18) show the same phenotype, multidisciplinary examinations and follow-up seem to be important to monitor evolving and developing clinical manifestations and to predict prognosis in advance associated with the specific genes of 18p breakpoint regions.

Presentation of an Infant with Chromosome 18p Deletion Syndrome and Asymmetric Septal Hypertrophy

The frequency of 18p deletion syndrome is estimated to be ∼1/50,000 live births and is more commonly associated with certain clinical features including short stature, intellectual disability, and facial dysmorphism. Physical examination of our patient revealed a short stature, intellectual disability, facial dysmorphism (microcephaly, ptosis, epicanthus, low nasal bridge, protruding ears, long philtrum, and thin lips), and clinodactyly of the fifth finger. The peripheral karyotype was 46, XX, del (18) (p11.32p11.2). DNA microarray analysis revealed a de novo 13.9-Mb deletion at 18p11.32p.11.21. Echocardiography revealed asymmetric septal hypertrophy. Congenital cardiac abnormalities are present very rarely in this syndrome. This finding suggests that one locus or loci that play a role in cardiac development is located in this chromosomal region. Although rare, cardiac hypertrophies should be kept in mind when evaluating a patient with phenotypic anomalies and genetic results compatible with an 18p deletion syndrome.

[Congenital hypopituitarism with monosomy of chromosome 18]

Congenital hypopituitarism is a rare disease. It can be caused by isolated inborn defects of the pituitary, gene mutations (PROP1, PIT1), and chromosomal abnormalities.Deletions of chromosome 18 (De Grouchy syndrome types 1 and 2) are a group of rare genetic diseases with a frequency of 1:50,000. Hypopituitarism in these syndromes is detected in from 13 to 56% of cases and depends on the size and location of the deleted segment.We have described a series of clinical cases of patients with congenital hypopituitarism due to deletions in chromosome 18. All children had a characteristic dysmorphic features and delayed mental and speech development. Within first months of life, patients developed muscular hypotension, dysphagia, and respiratory disorders. The patients had various congenital malformations in combination with hypopituitarism (isolated growth hormone deficiency and multiple pituitaryhormone deficiencies). In the neonatal period, there were the presence of hypoglycemia in combination with cholestasis.Hormone replacement therapy led to rapid relief of symptoms.Сhromosomal microarray analysis in 2 patients allowed us to identify exact location of deleted area and deleted genes and optimize further management for them.

Human Chromosome 18 and Acrocentrics: A Dangerous Liaison

The presence of thousands of repetitive sequences makes the centromere a fragile region subject to breakage. In this study we collected 31 cases of rearrangements of chromosome 18, of which 16 involved an acrocentric chromosome, during genetic screening done in three centers. We noticed a significant enrichment of reciprocal translocations between the centromere of chromosome 18 and the centromeric or pericentromeric regions of the acrocentrics. We describe five cases with translocation between chromosome 18 and an acrocentric chromosome, and one case involving the common telomere regions of chromosomes 18p and 22p. In addition, we bring evidence to support the hypothesis that chromosome 18 preferentially recombines with acrocentrics: (i) the presence on 18p11.21 of segmental duplications highly homologous to acrocentrics, that can justify a NAHR mechanism; (ii) the observation by 2D-FISH of the behavior of the centromeric regions of 18 respect to the centromeric regions of acrocentrics in the nuclei of normal subjects; (iii) the contact analysis among these regions on published Hi-C data from the human lymphoblastoid cell line (GM12878).

The genotype and phenotype of chromosome 18p deletion syndrome: Case series

RATIONALE

The chromosome 18p deletion syndrome is a syndrome with a deletion of all or a portion of the short arm of the chromosome 18. The phenotypes of the chromosome 18p deletion syndrome vary widely among individuals due to differences in size and breakpoints and the involved genes on the deletions. Given the varied and untypical clinical presentation of this syndrome, the prenatal diagnosis of the syndrome still presents as a challenge.

PATIENT CONCERNS

We described 4 China cases with different chromosomal breakpoints. In case 1, a woman who with mild phenotypes gave birth to a severely deformed fetus. Three other cases were for prenatal diagnosis. Their phenotypes are the increased nuchal translucency (INT) and the noninvasive prenatal testing (NIPT) indicated deletions on the chromosome 18p and severe hydronephrosis respectively.

DIAGNOSIS

The 4 cases were diagnosed with chromosome 18p deletion syndrome through karyotype analysis and array-based comparative genomic hybridization (array-CGH).

INTERVENTIONS

Karyotype analysis and array-based comparative genomic hybridization were used to analyze the abnormal chromosome.

OUTCOMES

Case 1 and case 2 revealed 11.51 and 12.39 Mb deletions in 18p11.32p11.21. Case 3 revealed 7.1 Mb deletions in 18p11.3218p11.23. Case 4 revealed 9.9 Mb deletions in 18p11.3218p11.22.

LESSONS

In our report, we are the first to report that mother and progeny who have the same chromosomal breakpoint have different phenotypes, significantly. In addition, we found a new phenotype of chromosome 18p deletion syndrome in fetus, which can enrich the phenotypes of this syndrome in the prenatal diagnosis. Finally, we demonstrate that the individuals with different chromosomal breakpoints of 18p deletion syndrome have different phenotypes. On the other hand, the individuals with the same chromosomal breakpoints of 18p deletion syndrome may also have remarkably different phenotypes.

Discovery of a Chinese familial deletion 18p syndrome due to a false positive result on noninvasive prenatal testing

Clinical manifestations of deletion 18p syndrome vary a lot, which makes it easily overlooked in the clinical practice. Familial transmission of deletion 18p syndrome is rare. We report a Chinese familial deletion 18p syndrome, which was diagnosed by anatomizing the underlying reason for the discrepancy between noninvasive prenatal testing (NIPT) and prenatal diagnosis. A 35-year-old pregnant woman was recruited to our center owing to the abnormal NIPT result with a high risk of chromosome 18 monosomy. However, the karyotype of the fetus was normal after amniocentesis. Further analysis indicated that the pregnant woman herself had an abnormal karyotype of 46,XX,del(18)(p11.2), (arr18p11.32p11.21[136,227-15,099,116]×1) and her first 12-year-old son had got the same deletion of 18p as her. A distinct phenotype variability was noted although they share identical deletion. We consider that adequate clinical genetic counseling is vital for women with adverse pregnancy history before getting pregnant. Maternal CNVs may be one of the main causes of the false-positive result on NIPT. NIPT, especially extended NIPT may provide extra valuable evidence when used as routine prenatal screening method.

An experience in prenatal diagnosis via QF-PCR of a female child with a 9.9 Mb pure deletion at 18p11.32-11.22

Quantitative Fluorescent - Polymerase Chain Reaction (QF-PCR) is a rapid prenatal diagnosis test for 21, 18, 13 and sex chromosomal aneuploidy detection. However, it could not detect partial trisomy or partial monosomy of those chromosomes. Here, we report a 19-month-old Vietnamese female with a 9.9 Mb pure deletion of chromosome 18 at 18p11.32-11.22 confirmed by next generation sequencing. The patient was short statured with facial dysmorphic features as well as motor skill and speech delays. First trimester screening showed high risk of trisomy 21 with only increased nuchal translucency (NT 3.9 mm) by ultrasound as an indication. Prenatal diagnosis by QF-PCR from amniotic DNA revealed normal disomy. Noticeably, two short tandem repeat (STR) markers D18S391 and D18S976 located on 18p exhibited uninformative patterns (one peak). Thus, our case suggested that the combination of both D18S391 and D18S976 markers with uninformative patterns in QF-PCR for prenatal diagnosis and increased NT in the first trimester ultrasound may be a significant indication of 18p monosomy.

Prenatal Diagnosis of a De Novo Partial Trisomy 6q and Partial Monosomy 18p Associated with Cephalocele: A Case Report

A 28-year-old woman underwent amniocentesis at 18 weeks’ gestation upon detection of increased fetal nuchal fold and parietal cephalocele on the second trimester ultrasound examination. Prenatal microarray showed a de novo unbalanced translocation resulting in a gain in 6q and loss in 18p. A female infant was delivered at 38 weeks’ gestation. At birth, cephalocele and webbed neck were noted as major dysmorphic features. The case presented here shows how a combination of different genetic studies is used to accurately elucidate a chromosomal anomaly in a prenatal setting.

The Consequences of Abnormal Gene Dosage: Lessons from Chromosome 18

Accurate interpretation of genomic copy number variation (CNV) remains a challenge and has important consequences for both congenital and late-onset disease. Hemizygosity dosage characterization of the genes on chromosome 18 reveals a spectrum of outcomes ranging from no clinical effect, to risk factors for disease, to both low- and high-penetrance disease. These data are important for accurate and predictive clinical management. Additionally, the potential mechanisms of reduced penetrance due to dosage compensation are discussed as a key to understanding avenues for potential treatment. This review describes the chromosome 18 findings, and discusses the molecular mechanisms that allow haploinsufficiency, reduced penetrance, and dosage compensation.

Prenatal diagnosis and molecular cytogenetic characterization of partial dup(18q)/del(18p) due to a paternal pericentric inversion 18 in a fetus with multiple anomalies

OBJECTIVE

We present prenatal diagnosis of rec(18)dup(18q)inv(18)(p11.2q21.2)pat owing to paternal pericentric inversion in a fetus.

CASE REPORT

A 37-year-old woman was diagnosed with multiple anomalies on a prenatal ultrasound scan at 17 weeks and 5 days of gestation. She underwent amniocentesis at 20 weeks and 2 days. Conventional karyotyping of amniocyte showed 46, XX, der(18). She was thus referred for genetic counseling; cytogenetic analysis revealed a 46, XY karyotype, inv(18)(p11.2q21.2), of the father. Therefore, based on the results of the father, the fetal karyotype was defined as 46, XX, rec(18)dup(18q)inv(18)(p11.2q21.2)pat. Array comparative genomic hybridization of amniocytes to obtain specific information showed a 3-Mb deletion of 18p11.31p11.32 (136227_3100353)x1 and a 23.7-Mb duplication of 18q21.31-q23 (54222717_77957375) × 3.

CONCLUSION

Maternal serum screening produces normal results for 18p-/18q+ syndrome, but it can be diagnosed by fluorescent in situ hybridization, quantitative-fluorescent polymerase chain reaction, or array comparative genomic hybridization test by observing abnormal findings on ultrasound.

A case of prenatal diagnosis of 18p deletion syndrome following noninvasive prenatal testing

Background

Chromosome 18p deletion syndrome is a disease caused by the complete or partial deletion of the short arm of chromosome 18, there were few cases reported about the prenatal diagnosis of 18p deletion syndrome. Noninvasive prenatal testing (NIPT) is widely used in the screening of common fetal chromosome aneuploidy. However, the segmental deletions and duplications should also be concerned. Except that some cases had increased nuchal translucency or holoprosencephaly, most of the fetal phenotype of 18p deletion syndrome may not be evident during the pregnancy, 18p deletion syndrome was always accidentally discovered during the prenatal examination.

Case presentations

In our case, we found a pure partial monosomy 18p deletion during the confirmation of the result of NIPT by copy number variation sequencing (CNV-Seq). The result of NIPT suggested that there was a partial or complete deletion of X chromosome. The amniotic fluid karyotype was normal, but result of CNV-Seq indicated a 7.56 Mb deletion on the short arm of chromosome 18 but not in the couple, which means the deletion was de novo deletion. Finally, the parents chose to terminate the pregnancy.

Conclusions

To our knowledge, this is the first case of prenatal diagnosis of 18p deletion syndrome following NIPT.NIPT combined with ultrasound may be a relatively efficient method to screen chromosome microdeletions especially for the 18p deletion syndrome.

Mutation analysis of SLC37A4 in a patient with glycogen storage disease-type Ib

Objective

The aim of the study was to investigate the relationship between SLC37A4 gene mutation and clinical phenotype in a patient with glycogen storage disease-type I.

Methods

The clinical data of one patient with glycogen storage disease-type I accumulation syndrome and the results of SLC37A4 gene testing were analyzed. DNA from peripheral blood was used to analyze the SLC37A4 mutations of the patient and his parents.

Results

The patient carried a compound heterozygous mutation of SLC37A4, his mother was heterozygous for the c.572C > T (p.P191L) mutation, and his father was heterozygous for the c.359C > T (p.P120L) mutation.

Conclusion

The patient had two gene mutations: c.359C > T (p.P120L), which is closely related to glycogen storage disease-type I, and c.572C > T (p.P191L), which is a known mutation in the disease.

SMCHD1 is involved in de novo methylation of the DUX4-encoding D4Z4 macrosatellite

The DNA methylation epigenetic signature is a key determinant during development. Rules governing its establishment and maintenance remain elusive especially at repetitive sequences, which account for the majority of methylated CGs. DNA methylation is altered in a number of diseases including those linked to mutations in factors that modify chromatin. Among them, SMCHD1 (Structural Maintenance of Chromosomes Hinge Domain Containing 1) has been of major interest following identification of germline mutations in Facio-Scapulo-Humeral Dystrophy (FSHD) and in an unrelated developmental disorder, Bosma Arhinia Microphthalmia Syndrome (BAMS). By investigating why germline SMCHD1 mutations lead to these two different diseases, we uncovered a role for this factor in de novo methylation at the pluripotent stage. SMCHD1 is required for the dynamic methylation of the D4Z4 macrosatellite upon reprogramming but seems dispensable for methylation maintenance. We find that FSHD and BAMS patient's cells carrying SMCHD1 mutations are both permissive for DUX4 expression, a transcription factor whose regulation has been proposed as the main trigger for FSHD. These findings open new questions as to what is the true aetiology for FSHD, the epigenetic events associated with the disease thus calling the current model into question and opening new perspectives for understanding repetitive DNA sequences regulation.

Prenatal diagnosis of de novo monosomy 18p deletion syndrome by chromosome microarray analysis: Three case reports

RATIONALE

Monosomy 18p deletion syndrome refers to a rare chromosomal disorder resulting from the part deletion of the short arm of chromosome 18. Prenatal diagnosis of de novo 18p deletion syndrome is a challenge due to its low incidence and untypical prenatal clinical presentation.

PATIENT CONCERNS

Three cases received amniocentesis due to increased nuchal translucency (INT), high risk for Down syndrome, and INT combined intrauterine growth retardation (IUGR), respectively.

DIAGNOSIS

The 3 cases were diagnosed with de novo monosomy 18p deletion syndrome by amniocentesis and chromosome microarray analysis (CMA).

INTERVENTIONS

Karyotype analysis and CMA were used to analyze the abnormal chromosome.

OUTCOMES

Case 1 and case 2 revealed 13.87 and 12.68 Mb deletions by array-CGH analysis, respectively. Case 3 revealed 6.9 Mb deletions in 18p11.32p11.31 and 7.5 Mb deletions in 18p11.23p11.21 by single nucleotide polymorphism array. All of the pregnancies were terminated due to the abnormal chromosome.

LESSONS

The fetal phenotype of monosomy 18p deletion syndrome shows great variability and may not be evident during the pregnancy. CMA may be served as an effective tool for the diagnosis of prenatal monosomy 18p deletion syndrome diagnosis.

Intellectual, adaptive and behavioural characteristics in four patients with 18p deletion syndrome

BACKGROUND

The association of behavioural phenotype assessment with cytogenomic characterisation may provide a better comprehension of genotype-phenotype correlations in syndromes caused by chromosomal abnormalities, such as 18p deletion syndrome.

METHOD

We report on four Brazilian patients with 18p deletion syndrome characterised by cytogenomic techniques and detailed neuropsychological evaluation. Intellectual, adaptive and behavioural characteristics were assessed through the Wechsler's Scales, the Vineland-II Scale and the Child Behaviour Checklist, respectively. Socio-economic measures including main caretaker educational level and family income as defined by Brazilian criteria for social class classification were also collected to evaluate a possible contribution of environmental factors in neurocognitive variability.

RESULTS

Two out of four patients showed intellectual disability (IQ < 70). Wechsler's scale results suggest that in our sample, interpretation of social situations based on observation of non-verbal behaviour constitute a cognitive strength while judgement of social rules and language skills associated with word knowledge and verbal fluency may be a cognitive weakness. Concerning adaptive behaviour, motor and socialisation domains showed to better develop than communication and daily living skills on the Vineland-II Scale. Only one patient presented internalising behavioural problems based on the Child Behaviour Checklist. Our results also suggested that socio-economic status may contribute to overall patient development.

CONCLUSION

Our results suggest that some 18p deletion syndrome patients may present average intellectual performance and that the segment deletion size and some families' socio-economic conditions may influence cognitive development.

A case of de novo 18p deletion syndrome with panhypopituitarism

Deletion on the short arm of chromosome 18 is a rare disorder characterized by intellectual disability, growth retardation, and craniofacial malformations (such as prominent ears, microcephaly, ptosis, and a round face). The phenotypic spectrum is wide, encompassing a range of abnormalities from minor congenital malformations to holoprosencephaly. We present a case of a 2-year-old girl with ptosis, a round face, broad neck with low posterior hairline, short stature, and panhypopituitarism. She underwent ventilation tube insertion for recurrent otitis media with effusion. Brain magnetic resonance imaging showed an ectopic posterior pituitary gland and a shallow, small sella turcica with poor visualization of the pituitary stalk. Cytogenetic and chromosomal microarray analysis revealed a de novo deletion on the short arm of chromosome 18 (arr 18p11.32p11.21[136,227-15,099,116]x1). She has been treated with recombinant human growth hormone (GH) therapy since the age of 6 months after diagnosis of GH deficiency. Her growth rate has improved without any side effects from the GH treatment. This case expands the phenotypic spectrum of 18p deletion syndrome and emphasizes the positive impact of GH therapy on linear growth in this syndrome characterized by growth deficiency. Further studies are required to define the genotype-phenotype correlation according to size and loci of the deletion in 18p deletion syndrome and to predict prognosis.

A 13-year-old girl with 18p deletion syndrome presenting Turner syndrome-like clinical features of short stature, short webbed neck, low posterior hair line, puffy eyelids and increased carrying angle of the elbows

OBJECTIVE

We report a 13-year-old girl with 18p deletion syndrome presenting Turner syndrome-like clinical features.

CASE REPORT

A 13-year-old girl was referred for genetic counseling of Turner syndrome-like clinical features of short stature, short webbed neck, low posterior hair line, puffy eyelids and increased carrying angle of the elbows. The girl also had mild intellectual disability, psychomotor developmental delay, speech disorder, high-arched palate, hypertelorism and mid-face hypoplasia. Cytogenetic analysis of the girl revealed a karyotype of 46,XX,del(18) (p11.2). The parental karyotypes were normal. Array comparative genomic hybridization analysis on the DNA extracted from the peripheral blood revealed a 13.93-Mb deletion of 18p11.32-p11.21 or arr 18p11.32p11.21 (148,993-14,081,858) × 1.0 [GRCh37 (hg19)] encompassing 52 Online Mendelian Inheritance in Man (OMIM) genes including USP14, TYMS, SMCHD1, TGIF1, LAMA1, TWSG1, GNAL and PTPN2. Polymorphic DNA marker analysis revealed a maternal origin of the deletion.

CONCLUSION

Females with Turner syndrome-like clinical features in association with intellectual disability, facial dysmorphism and psychomotor developmental delay should be suspected of having chromosome deletion syndromes.

Chromosome 18 gene dosage map 2.0

In 2009, we described the first generation of the chromosome 18 gene dosage maps. This tool included the annotation of each gene as well as each phenotype associated region. The goal of these annotated genetic maps is to provide clinicians with a tool to appreciate the potential clinical impact of a chromosome 18 deletion or duplication. These maps are continually updated with the most recent and relevant data regarding chromosome 18. Over the course of the past decade, there have also been advances in our understanding of the molecular mechanisms underpinning genetic disease. Therefore, we have updated the maps to more accurately reflect this knowledge. Our Gene Dosage Map 2.0 has expanded from the gene and phenotype maps to also include a pair of maps specific to hemizygosity and suprazygosity. Moreover, we have revamped our classification from mechanistic definitions (e.g., haplosufficient, haploinsufficient) to clinically oriented classifications (e.g., risk factor, conditional, low penetrance, causal). This creates a map with gradient of classifications that more accurately represents the spectrum between the two poles of pathogenic and benign. While the data included in this manuscript are specific to chromosome 18, they may serve as a clinically relevant model that can be applied to the rest of the genome.

Enrichment of rare copy number variation in children with developmental language disorder

Developmental language disorder (DLD) is a common neurodevelopmental disorder with largely unknown etiology. Rare copy number variants (CNVs) have been implicated in the genetic architecture of other neurodevelopmental disorders (NDDs), which have led to clinical genetic testing recommendations for these disorders; however, the evidence is still lacking for DLD. We analyzed rare and de novo CNVs in 58 probands with severe DLD, their 159 family members and 76 Swedish typically developing children using high-resolution microarray. DLD probands had larger rare CNVs as measured by total length (P = .05), and average length (P = .04). In addition, the rate of rare CNVs overlapping coding genes was increased (P = .03 and P = .01) and in average more genes were affected (P = .006 and P = .03) in the probands and their siblings, respectively. De novo CNVs were found in 4.8% DLD probands (2/42) and 2.4% (1/42) siblings. Clinically significant CNVs or chromosomal anomalies were found in 6.9% (4/58) of the probands of which 2 carried 16p11.2 deletions. We provide further evidence that rare CNVs contribute to the etiology of DLD in loci that overlap with other NDDs. Based on our results and earlier literature, families with DLD should be offered molecular genetic testing as a routine in their clinical follow-up.

The Chromosome 18 Clinical Resource Center

BACKGROUND

The Chromosome 18 Clinical Research Center has created a pediatrician-friendly virtual resource center for managing patients with chromosome 18 abnormalities. To date, children with rare chromosome abnormalities have been cared for either symptomatically or palliatively as a reaction to the presenting medical problems. As we enter an era of genomic-informed medicine, we can provide children, even those with individually unique chromosome abnormalities, with proactive medical care and management based on the most contemporary data on their specific genomic change. It is problematic for practicing physicians to obtain and use the emerging data on specific genes because this information is derived from diverse sources (e.g., animal studies, case reports, in vitro explorations) and is often published in sources that are not easily accessible in the clinical setting.

METHODS

The Chromosome 18 Clinical Resource Center remedies this challenging problem by curating and synthesizing the data with clinical implications. The data are collected from our database of over 26 years of natural history and medical data from over 650 individuals with chromosome 18 abnormalities.

RESULTS

The resulting management guides and video presentations are a first edition of this collated data specifically oriented to guide clinicians toward the optimization of care for each child.

CONCLUSION

The chromosome 18 data and guides also serve as models for an approach to the management of any individual with a rare chromosome abnormality of which there are over 1,300 born every year in the US alone.

Monosomy 18p is a risk factor for facioscapulohumeral dystrophy

BACKGROUND

18p deletion syndrome is a rare disorder caused by partial or full monosomy of the short arm of chromosome 18. Clinical symptoms caused by 18p hemizygosity include cognitive impairment, mild facial dysmorphism, strabismus and ptosis. Among other genes, structural maintenance of chromosomes flexible hinge domain containing 1 (SMCHD1) is hemizygous in most patients with 18p deletions. Digenic inheritance of a SMCHD1 mutation and a moderately sized D4Z4 repeat on a facioscapulohumeral muscular dystrophy (FSHD) permissive genetic background of chromosome 4 can cause FSHD type 2 (FSHD2).

OBJECTIVES

Since 12% of Caucasian individuals harbour moderately sized D4Z4 repeats on an FSHD permissive background, we tested if people with 18p deletions are at risk of developing FSHD.

METHODS

To test our hypothesis we studied different cellular systems originating from individuals with 18p deletions not presenting FSHD2 phenotype for transcriptional and epigenetic characteristics of FSHD at D4Z4. Furthermore, individuals with an idiopathic muscle phenotype and an 18p deletion were subjected to neurological examination.

RESULTS

Primary fibroblasts hemizygous for SMCHD1 have a D4Z4 chromatin structure comparable with FSHD2 concomitant with DUX4 expression after transdifferentiation into myocytes. Neurological examination of 18p deletion individuals from two independent families with a moderately sized D4Z4 repeat identified muscle features compatible with FSHD.

CONCLUSIONS

18p deletions leading to haploinsufficiency of SMCHD1, together with a moderately sized FSHD permissive D4Z4 allele, can associate with symptoms and molecular features of FSHD. We propose that patients with 18p deletion should be characterised for their D4Z4 repeat size and haplotype and monitored for clinical features of FSHD.

Genotype-Phenotype Analysis, Neuropsychological Assessment, and Growth Hormone Response in a Patient with 18p Deletion Syndrome

18p deletion syndrome is a rare chromosomal disease caused by deletion of the short arm of chromosome 18. By using cytogenetic and SNP array analysis, we identified a girl with 18p deletion syndrome exhibiting craniofacial anomalies, intellectual disability, and short stature. G-banding analysis of metaphase cells revealed an abnormal karyotype 46,XX,del(18)(p10). Further, SNP array detected a 15.3-Mb deletion at 18p11.21p11.32 (chr18:12842-15375878) including 61 OMIM genes. Genotype-phenotype correlation analysis showed that clinical manifestations of the patient were correlated with LAMA1, TWSG1, and GNAL deletions. Her neuropsychological assessment test demonstrated delay in most cognitive functions including impaired mathematics, linguistic skills, visual motor perception, respond speed, and executive function. Meanwhile, her integrated visual and auditory continuous performance test (IVA-CPT) indicated a severe comprehensive attention deficit. At age 7 and 1/12 years, her height was 110.8 cm (-2.5 SD height for age). Growth hormone (GH) treatment was initiated. After 27 months treatment, her height was increased to 129.6 cm (-1.0 SD height for age) at 9 and 4/12 years, indicating an effective response to GH treatment.

Rheumatoid arthritis in an adult patient with mosaic distal 18q-, 18p- and ring chromosome 18

Ring chromosome 18 has a highly variable phenotype, depending on the extent of distal arm deletions. It is most commonly presented as a combination of 18p- and distal 18q- syndrome. IgA deficiency and autoimmune diseases have been previously described in these patients. Seven cases of juvenile rheumatoid arthritis (JRA) have been reported. Here we report the first case of late onset rheumatoid arthritis (RA) in a 32 year old Dominican woman with hypothyroidism, vitiligo, IgA deficiency, interstitial lung disease (ILD), cystic bronchiectasis, and features consistent with ringed 18, 18p- and distal 18q syndrome.  The multiple autoimmune findings in our patient lends further support to the idea of loci on chromosome 18 playing a role in autoimmune disease expression. Late onset RA and ILD in a patient with chromosome 18 abnormalities are novel findings and are additional conditions to be aware of in this population.

A Peruvian Child with 18p-/18q+ Syndrome and Persistent Microscopic Hematuria

Chromosome 18 pericentric inversion carriers could have offspring with recombinant chromosomes, leading to patients with clinical variable manifestations. Patients with 18p-/18q+ rearrangements share some clinical characteristics, while other characteristics differ. Factors for such divergence include the length of the inverted segment, among others. Here, we describe a Peruvian child with dysmorphic features, intellectual disability persistent microscopic hematuria, aortic pseudocoarctation, and descending aorta arteritis, among others. Karyotype analysis of family members determined the mother as the carrier of a pericentric inversion: 18[inv(18)(p11.2q21.3)]. This child carries a recombinant chromosome 18, with chromosomal microarray analysis detecting two genomic imbalances in patient's chromosome 18: one duplicated region and one deleted segment in the large and the short arms, respectively. Persistent microscopic hematuria has not been reported among 18p-/18q+ phenotypes. Our patient elucidates that other factors play significant and yet unknown roles for not fulfilling the proposed genotype-phenotype correlation associated with hemizygosity in this type of recombinant chromosome 18 or presenting these features as the patient ages.

A case of 18p deletion syndrome after blepharoplasty

Objective

The deletion of the short arm of chromosome 18 is thought to be one of the rare chromosomal aberrations. Here, we report a case to review this disease.

Case report

The proband is a five-and-a-half-year-old girl who has had phenotypes manifested mainly by ptosis, broad face, broad neck with low posterior hairline, mental retardation, short stature, and other malformations. Chromosomal analysis for her mother showed a normal karyotype. Her father and younger brother were phenotypically normal.

Result

Phenotypical features were quite similar throughout other cases and in accordance with the usual phenotype of del(18p) suggested within the same cases and among the del(18p) cases described. She underwent blepharoplasty, which improved her appearance.

Conclusion

18p deletion syndrome is diagnosed by gene analysis. Plastic surgeries for improving the appearance might be an option for these patients.

A 18p11.23-p11.31 microduplication in a boy with psychomotor delay, cerebellar vermis hypoplasia, chorioretinal coloboma, deafness and GH deficiency

Background

Rearrangements involving the short arm of chromosome 18 have been extensively described. Here we report a microduplication of 320.5–431.5 Kb at 18p11.31-p11.23 in a 10 year-old boy.

Case presentation

In a 10 year-old boy with moderate psychomotor delay, hypoplasia of the cerebellar vermis, chorioretinal coloboma, deafness and growth hormone deficiency (GHD), an interstitial microduplication at 18p11.31-p11.23 was identified by array-CGH. This maternally inherited microduplication, encompasses three genes, namely ARHGAP28, LINC00668 and LAMA1 (a gene involved in cerebellum and retinal development).

Conclusions

The genotype-phenotype is discussed with particular attention to the LAMA1 gene, although it is difficult, as in many other similar situations, to assess the causality of the detected duplication in the absence of further studies aiming to explore the presence of co-occurring variants that could explain the incomplete penetrance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-016-0298-9) contains supplementary material, which is available to authorized users.

Classical and non-classical causes of GH deficiency in the paediatric age

Growth hormone deficiency (GHD) may result from a failure of hypothalamic GHRH production or release, from congenital disorders of pituitary development, or from central nervous system insults including tumors, surgery, trauma, radiation or infiltration from inflammatory diseases. Idiopathic, isolated GHD is the most common sporadic form of hypopituitarism. GHD may also occur in combination with other pituitary hormone deficiencies, and is often referred to as hypopituitarism, combined pituitary hormone deficiency (CPHD), multiple pituitary hormone deficiency (MPHD) or panhypopituitarism. Children without any identifiable cause of their GHD are commonly labeled as having idiopathic hypopituitarism. MRI imaging is the technique of choice in the diagnosis of children with hypopituitarism. Marked differences in MRI pituitary gland morphology suggest different etiologies of GHD and different prognoses. Pituitary stalk agenesis and ectopic posterior pituitary (EPP) are specific markers of permanent GHD, and patients with these MRI findings show a different clinical and endocrine outcome compared to those with normal pituitary anatomy or hypoplastic pituitary alone. Furthermore, the classic triad of ectopic posterior pituitary gland, pituitary stalk hypoplasia/agenesis, and anterior pituitary gland hypoplasia is generally associated with permanent GHD. T2 DRIVE images aid in the identification of pituitary stalk without the use of contrast medium administration. Future developments in imaging techniques will undoubtedly reveal additional insights. Mutations in a number of genes encoding transcription factors - such as HESX1, SOX2, SOX3, LHX3, LHX4, PROP1, POU1F1, PITX, GLI3, GLI2, OTX2, ARNT2, IGSF1, FGF8, FGFR1, PROKR2, PROK2, CHD7, WDR11, NFKB2, PAX6, TCF7L1, IFT72, GPR161 and CDON - have been associated with pituitary dysfunction and abnormal pituitary gland development; the correlation of genetic mutations to endocrine and MRI phenotypes has improved our knowledge of pituitary development and management of patients with hypopituitarism, both in terms of possible genetic counseling, and of early diagnosis of evolving anterior pituitary hormone deficiencies.

Anterior Pituitary Aplasia in an Infant with Ring Chromosome 18p Deletion

We present the first reported case of an infant with 18p deletion syndrome with anterior pituitary aplasia secondary to a ring chromosome. Endocrine workup soon after birth was reassuring; however, repeat testing months later confirmed central hypopituitarism. While MRI reading initially indicated no midline defects, subsequent review of the images confirmed anterior pituitary aplasia with ectopic posterior pituitary. This case demonstrates how deletion of genetic material, even if resulting in a chromosomal ring, still results in a severe syndromic phenotype. Furthermore, it demonstrates the necessity of close follow-up in the first year of life for children with 18p deletion syndrome and emphasizes the need to verify radiology impressions if there is any doubt as to the radiologic findings.