The spectrum of growth abnormalities in children with 18q deletions

Unusual Endocrinopathies in 18q Deletion Syndrome: Pseudoparathyroidism and Hyper-/Hypo-Thyroidism

Objective

To describe new and unusual endocrinopathies in children with de novo 18q deletion (18q-) syndrome.

Methods

We describe 2 patients who have atypical thyroid conditions and 1 who also developed symptomatic hypocalcemia.

Results

The first patient developed hyperthyroidism at the age of 3 years, with a free thyroxine level of 3.9 (range, 0.8-1.8) ng/dL. Thyroid peroxidase antibodies were 262 (range, 0-32) IU/mL, and thyroid-stimulating immunoglobulin antibodies were 384% (range, 0-139%). On low-dose methimazole treatment, she developed hypothyroidism. Thyroid-stimulating hormone (TSH) level was 163 (range, 0.4-4.5) mIU/mL. Moreover, she later developed growth hormone deficiency. The second patient developed hypothyroidism at the age of 4 years, with a TSH level of 46 mIU/mL. However, TSH remained elevated at levels of 10 to 24 mIU/mL for 3 years, despite appropriate treatment, suggesting TSH resistance. She then developed hypocalcemic seizures and was diagnosed with pseudohypoparathyroidism. Her total calcium level was 6.6 (range, 8.5-10.5) mg/dL and parathyroid hormone level was 432 (range, 15-65) pg/dL.

Conclusion

The first patient had a mixed picture of autoimmune hypothyroidism and hyperthyroidism, requiring a combination of methimazole and levothyroxine to achieve a euthyroid state. For the second patient, the mild TSH resistance was possibly the early suggestion of a parathyroid hormone resistant state. Although growth hormone deficiency and hypothyroidism are common in patients with 18q- syndrome, the occurrence of hyperthyroidism due to Graves’ disease with the coexistence of Hashimoto’s hypothyroidism is rare. Pseudohypoparathyroidism has not yet been reported in patients with 18q- syndrome.

Clinical Characteristics and Long-Term Recombinant Human Growth Hormone Treatment of 18q- Syndrome: A Case Report and Literature Review

BACKGROUND

18q- syndrome is a rare chromosomal disease caused by the deletion of the long arm of chromosome 18. Some cases with 18q- syndrome can be combined with growth hormone deficiency (GHD), but data on the efficacy of recombinant human growth hormone (rhGH) treatment in 18q- syndrome are limited.

METHODS

Here, we report one case of 18q- syndrome successfully treated with long-term rhGH supplement. Previously reported cases in the literature are also reviewed to investigate the karyotype-phenotype relationship and their therapeutic response to rhGH.

RESULTS

A 7.9-year-old girl was referred for evaluation for short stature. Physical exam revealed proportionally short stature with a height of 111.10 cm (-3.02 SD score (SDS)), low-set ears, a high-arched palate, a small jaw, webbed neck, widely spaced nipples, long and tapering fingers, and cubitus valgus. Thyroid function test indicated subclinical hypothyroidism. The peak value of growth hormone was 10.26 ng/ml in the levodopa provocation test. Insulin-like growth factor 1 (IGF-1) was 126 ng/ml (57-316 ng/ml). Other laboratory investigations, including complete blood cell count, liver and kidney function, gonadal function, serum adrenocorticotropin levels, and serum cortisol levels, were all within normal ranges. Karyotype analysis showed 46, XX, del (18) (q21). L-Thyroxine replacement and rhGH treatment were initiated and maintained in the following 7 years. At the age of 14.8, her height has reached 159.5 cm with a height SDS increase of 2.82 SDS (from -3.02 SDS to -0.20 SDS). No significant side effects were found during the treatment. The literature review indicated the average rhGH treatment duration of 16 patients was 5.9 ± 3.3 years, and the average height SDS significantly increased from -3.12 ± 0.94 SDS to -1.38 ± 1.29 SDS after the rhGH treatment (p < 0.0001).

CONCLUSION

The main clinical manifestations of 18q- syndrome include characteristic appearance, intellectual disability, and abnormal genital development. The literature review suggested a significant height benefit for short stature with 18q- syndrome from long-term rhGH treatment.

Identification of De Novo and Rare Inherited Copy Number Variants in Children with Syndromic Congenital Heart Defects

Congenital heart defects (CHDs) are the most common birth defects in neonatal life. CHDs could be presented as isolated defects or associated with developmental delay (DD) and/or other congenital malformations. A small proportion of cardiac defects are caused by chromosomal abnormalities or single gene defects; however, in a large proportion of cases no genetic diagnosis could be achieved by clinical examination and conventional genetic analysis. The development of genome wide array-Comparative Genomic Hybridization technique (array-CGH) allowed for the detection of cryptic chromosomal imbalances and pathogenic copy number variants (CNVs) not detected by conventional techniques. We investigated 94 patients having CHDs associated with other malformations and/or DD. Clinical examination and Echocardiography was done to all patients to evaluate the type of CHD. To investigate for genome defects we applied high-density array-CGH 2 × 400K (41 patients) and CGH/SNP microarray 2 × 400K (Agilent) for 53 patients. Confirmation of results was done using Fluorescent in situ hybridization (FISH) or qPCR techniques in certain cases. Chromosomal abnormalities such as trisomy 18, 13, 21, microdeletions: del22q11.2, del7q11.23, del18 (p11.32; p11.21), tetrasomy 18p, trisomy 9p, del11q24-q25, add 15p, add(18)(q21.3), and der 9, 15 (q34.2; q11.2) were detected in 21/94 patients (22%) using both conventional cytogenetics methods and array-CGH technique. Cryptic chromosomal anomalies and pathogenic variants were detected in 15/73 (20.5%) cases. CNVs were observed in a large proportion of the studied samples (27/56) (48%). Clustering of variants was observed in chromosome 1p36, 1p21.1, 2q37, 3q29, 5p15, 7p22.3, 8p23, 11p15.5, 14q11.2, 15q11.2, 16p13.3, 16p11.2, 18p11, 21q22, and 22q11.2. CGH/SNP array could detect loss of heterozygosity (LOH) in different chromosomal loci in 10/25 patients. Array-CGH technique allowed for detection of cryptic chromosomal imbalances that could not be detected by conventional cytogenetics methods. CHDs associated with DD/congenital malformations presented with a relatively high rate of cryptic chromosomal abnormalities. Clustering of CNVs in certain genome loci needs further analysis to identify candidate genes that may provide clues for understanding the molecular pathway of cardiac development.

Features of two cases with 18q deletion syndrome

The 18q Deletion syndrome is seen in 1 out of 10 000 live births. The main features of the syndrome are short stature, hearing loss, hypotonia, mental retardation, endocrine disorders and autoimmunity. Here, we present 2 patients with this syndrome admitted to our clinic who were found to have insulin resistance in addition to mental retardation, short stature, autoimmune thyroiditis and hearing loss. The need to perform a karyogram analysis in cases presenting with these features is emphasized.

Establishing a reference group for distal 18q-: clinical description and molecular basis

Although constitutional chromosome abnormalities have been recognized since the 1960s, clinical characterization and development of treatment options have been hampered by their obvious genetic complexity and relative rarity. Additionally, deletions of 18q are particularly heterogeneous, with no two people having the same breakpoints. We identified 16 individuals with deletions that, despite unique breakpoints, encompass the same set of genes within a 17.6-Mb region. This group represents the most genotypically similar group yet identified with distal 18q deletions. As the deletion is of average size when compared with other 18q deletions, this group can serve as a reference point for the clinical and molecular description of this condition. We performed a thorough medical record review as well as a series of clinical evaluations on 14 of the 16 individuals. Common functional findings included developmental delays, hypotonia, growth hormone deficiency, and hearing loss. Structural anomalies included foot anomalies, ear canal atresia/stenosis, and hypospadias. The majority of individuals performed within the low normal range of cognitive ability but had more serious deficits in adaptive abilities. Of interest, the hemizygous region contains 38 known genes, 26 of which are sufficiently understood to tentatively determine dosage sensitivity. Published data suggest that 20 are unlikely to cause an abnormal phenotype in the hemizygous state and five are likely to be dosage sensitive: TNX3, NETO1, ZNF407, TSHZ1, and NFATC. A sixth gene, ATP9B, may be conditionally dosage sensitive. Not all distal 18q- phenotypes can be attributed to these six genes; however, this is an important advance in the molecular characterization of 18q deletions.

Genome-wide association study identified CNP12587 region underlying height variation in Chinese females

Introduction

Human height is a highly heritable trait considered as an important factor for health. There has been limited success in identifying the genetic factors underlying height variation. We aim to identify sequence variants associated with adult height by a genome-wide association study of copy number variants (CNVs) in Chinese.

Methods

Genome-wide CNV association analyses were conducted in 1,625 unrelated Chinese adults and sex specific subgroup for height variation, respectively. Height was measured with a stadiometer. Affymetrix SNP6.0 genotyping platform was used to identify copy number polymorphisms (CNPs). We constructed a genomic map containing 1,009 CNPs in Chinese individuals and performed a genome-wide association study of CNPs with height.

Results

We detected 10 significant association signals for height (p<0.05) in the whole population, 9 and 11 association signals for Chinese female and male population, respectively. A copy number polymorphism (CNP12587, chr18:54081842-54086942, p = 2.41×10⁻⁴) was found to be significantly associated with height variation in Chinese females even after strict Bonferroni correction (p = 0.048). Confirmatory real time PCR experiments lent further support for CNV validation. Compared to female subjects with two copies of the CNP, carriers of three copies had an average of 8.1% decrease in height. An important candidate gene, ubiquitin-protein ligase NEDD4-like (NEDD4L), was detected at this region, which plays important roles in bone metabolism by binding to bone formation regulators.

Conclusions

Our findings suggest the important genetic variants underlying height variation in Chinese.

Chromosome abnormalities in Indonesian patients with short stature

Background

Short stature is associated with several disorders including wide variations of chromosomal disorders and single gene disorders. The objective of this report is to present the cytogenetic findings in Indonesian patients with short stature.

Methods

G-banding and interphase/metaphase FISH were performed on short stature patients with and without other clinical features who were referred by clinicians all over Indonesia to our laboratory during the year 2003–2009.

Results

The results of chromosomal analysis of ninety seven patients (mean age: 10.7 years old) were collected. The group of patients with other clinical features showed sex chromosome abnormalities in 45% (18/40) and autosomal abnormalities in 10% (4/40), whereas those with short stature only, 42.1% (24/57) had sex chromosome abnormalities and 1.75% (1/57) had autosomal abnormalities. The autosomal chromosomal abnormalities involved mostly subtelomeric regions. Results discrepancies between karyotype and FISH were found in 10 patients, including detection of low-level monosomy X mosaicism in 6 patients with normal karyotype, and detection of mosaic aneuploidy chromosome 18 in 1 patient with 45,XX,rob(13;14)(q10;q10).

Statistical analysis showed no significant association between the groups and the type of chromosomal abnormalities.

Conclusion

Chromosome abnormalities account for about 50% of the short stature patients. Wide variations of both sex and autosomal chromosomes abnormalities were detected in the study. Since three out of five patients had autosomal structural abnormalities involving the subtelomeric regions, thus in the future, subtelomeric FISH or even a more sensitive method such as genomic/SNP microarray is needed to confirm deletions of subtelomeric regions of chromosome 9, 11 and 18. Low-level mosaicism in normal karyotype patients indicates interphase FISH need to be routinely carried out in short stature patients as an adjunct to karyotyping.

Growth monitoring still has a place in selected populations of children

In 1998, a multiprofessional group developed a consensus on growth monitoring in the UK. While routine serial measurements were not recommended in healthy children, it is clear that there is a subset of children at increased risk of growth-modifying disease who may benefit from growth monitoring. This subset includes children with genetic disorders at increased risk of thyroid dysfunction. Symptoms and signs of thyroid dysfunction are non-specific in the early stages of disease and are easily mistaken for features of an underlying genetic disorder. In this article, we report the case of a 2.8-year-old girl with 18q deletion syndrome who was profoundly weak, hypotonic and poorly responsive at diagnosis of Grave's disease. She was tall and her bone age was 2 years advanced, indicating long-standing disease. Growth monitoring of this patient should have enabled earlier diagnosis and avoided a serious and potentially fatal episode.

Narrowing critical regions and determining penetrance for selected 18q- phenotypes

One of our primary goals is to help families who have a child with an 18q deletion anticipate medical issues in order to optimize their child's medical care. To this end we have narrowed the critical regions for four phenotypic features and determined the penetrance for each of those phenotypes when the critical region for that feature is hemizygous. We completed molecular analysis using oligo-array CGH and clinical assessments on 151 individuals with deletions of 18q and made genotype-phenotype correlations defining or narrowing critical regions. These nested regions, all within 18q22.3 to q23, were for kidney malformations, dysmyelination of the brain, growth hormone stimulation response failure, and aural atresia. The region for dysmyelination and growth hormone stimulation response failure were identical and was narrowed to 1.62 Mb, a region containing five known genes. The region for aural atresia was 2.3 Mb and includes an additional three genes. The region for kidney malformations was 3.21 Mb and includes an additional four genes. Penetrance rates were calculated by comparing the number of individuals hemizygous for a critical region with the phenotype to those without the phenotype. The kidney malformations region was 25% penetrant, the dysmyelination region was 100% penetrant, the growth hormone stimulant response failure region was 90% penetrant with variable expressivity, and the aural atresia region was 78% penetrant. Identification of these critical regions suggest possible candidate genes, while penetrance calculations begin to create a predictive phenotypic description based on genotype.

Case report of de novo dup(18p)/del(18q) and r(18) mosaicism

This is a report of a 27-year-old woman with an unusual de novo chromosomal abnormality. Mosaicism was identified in peripheral blood cells examined by standard G-bands by trypsin using Giemsa (GTG) analysis and fluorescence in situ hybridization (FISH) analysis with chromosome-18 region-specific probes, 46,XX,del(18)(pter --> q21.33:)[41], 46,XX,r(18)(::p11.21 --> q21.33::)[8], and 46,XX,der(18)(pter --> q21.33::p11.21 --> pter)[1]. On the other hand, the karyotype of periodontal ligament fibroblasts was nonmosaic, 46,XX, der(18)(pter --> q21.33::p11.21 --> pter)[50]. All cell lines appeared to be missing a portion of 18q (q21.33 --> qter). The pattern of the dup(18p)/del(18q) in the rod configuration raises the possibility of an inversion in chromosome 18 in one of the parents. However, no chromosomal anomaly was detected in either parent. The most probable explanation is that de novo rod and ring configurations arose simultaneously from an intrachromosomal exchange. The unique phenotype of this patient, which included primary hypothyroidism and primary hypogonadism, is discussed in relation to her karyotype.

Highly conserved non-coding sequences and the 18q critical region for short stature: a common mechanism of disease?

Background

Isolated growth hormone deficiency (IGHD) and multiple pituitary hormone deficiency (MPHD) are heterogeneous disorders with several different etiologies and they are responsible for most cases of short stature. Mutations in different genes have been identified but still many patients did not present mutations in any of the known genes. Chromosomal rearrangements may also be involved in short stature and, among others, deletions of 18q23 defined a critical region for the disorder. No gene was yet identified.

Methodology/Principal Findings

We now report a balanced translocation X;18 in a patient presenting a breakpoint in 18q23 that was surprisingly mapped about 500 Kb distal from the short stature critical region. It separated from the flanking SALL3 gene a region enriched in highly conserved non-coding elements (HCNE) that appeared to be regulatory sequences, active as enhancers or silencers during embryonic development.

Conclusion

We propose that, during pituitary development, the 18q rearrangement may alter expression of 18q genes or of X chromosome genes that are translocated next to the HCNEs. Alteration of expression of developmentally regulated genes by translocation of HCNEs may represent a common mechanism for disorders associated to isolated chromosomal rearrangements.