Genetics of Short Stature

Children With Idiopathic Short Stature: An Expanding Role for Genetic Investigation in Their Medical Evaluation

Short stature in children is a common reason for referral to a pediatric endocrinologist. Many genetic, nutritional, psychological, illness-related, and hormonal causes must be excluded before labeling as idiopathic. Idiopathic short stature is not a diagnosis, but rather describes a large, heterogeneous group of children, who are short and often slowly growing. As new testing paradigms become available, the pool of patients labeled as idiopathic will shrink, although most will have a polygenic cause. Given that many of the new diagnoses are involved in growth plate biology, physical examination should assess for subtle dysmorphology or disproportion of the skeleton that may indicate a heterozygous mutation that in its homozygous state would be apparent. When laboratory evaluations are negative, one may consider genetic testing, such as targeted gene or gene panel, comparative genomic hybridization, or whole exome or whole genome sequencing (respectively). With a known genetic diagnosis, targeted therapy may be possible rather than recombinant human growth hormone, where response is generally poorer than that for children with growth hormone deficiency, because the variety of diagnoses may have varying growth hormone sensitivity. A firm diagnosis has heuristic value: to truncate further diagnostic evaluation, alert the clinician to other possible comorbidities, inform the family for genetic counseling, and direct appropriate targeted therapy, if available.

Role of genetic investigation in the diagnosis of short stature in a cohort of Italian children

BACKGROUND

Short stature (SS) is defined as height more than 2 standard deviations below the mean for age and sex. Hypothyroidism, celiac disease, growth hormone deficiency, hormonal abnormalities, and genetic conditions are among its causes. A wide range of conditions often due to largely unknown genetic variants can elude conventional diagnostic workup.

AIM

We used next-generation sequencing (NGS) to better understand the etiology of SS in a cohort of Italian children.

PATIENTS AND METHODS

The study sample was 125 children with SS of unknown origin referred to our Institute between 2015 and 2021. All had undergone complete auxological and hormonal investigations to exclude common causes of SS. Genetic analysis was performed using a NGS panel of 104 genes. Clinical data were reviewed to clarify the pathogenicity of the variants detected.

RESULTS

In this cohort, 43 potentially causing variants were identified in 38 children. A syndromic genetic condition was diagnosed in 7: Noonan syndrome in 3, Leri-Weill syndrome in 3, and hypochondroplasia in 1. Moreover, 8 benign variants and other 37 like benign variants were found. In 88 children, 179 variants of uncertain significance (VUS) were identified. No variant was found in 16 children.

CONCLUSION

Genetic analysis is a useful tool in the diagnostic workup of patients with SS, in adapting management and treatment, and in identifying syndromes with mild atypical clinical features. The role of VUS should not be underestimated, particularly when multiple VUS with possible mutual worsening effects are present in the same child.

Clinical, genetic profile and therapy evaluation of 11 Chinese pediatric patients with Fanconi-Bickel syndrome

BACKGROUND

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder characterized by impaired glucose and galactose utilization as well as proximal renal tubular dysfunction.

METHODS

Clinical, biochemical, genetic, treatment, and follow-up data for 11 pediatric patients with FBS were retrospectively analysed.

RESULTS

Hepatomegaly (10/11), short stature (10/11) and hypophosphataemic rickets (7/11) were the most common initial symptoms. At diagnosis, all patients had decreased fasting blood glucose (FBG), plasma bicarbonate (HCO3-) and serum phosphorus, as well as elevated liver transaminases, alkaline phosphatase (AKP) and proximal renal tubular dysfunction. Two infant patients were misdiagnosed with transient neonatal diabetes mellitus. After therapy with uncooked cornstarch and conventional rickets treatment, remission of hepatomegaly was observed in all patients, with significant improvements in pre-prandial blood glucose, liver transaminases, triglyceride, plasma HCO3- and AKP (p < 0.05). At the last follow-up, 5/7 patients with elevated AKP had nephrocalcinosis. The mean height standard deviation score (Ht SDS) of eight patients with regular treatment increased from - 4.1 to -3.5 (p = 0.02). Recombinant human growth hormone (rhGH) was administered to 4/9 patients, but their Ht SDS did not improve significantly (p = 0.13). Fourteen variants of the SLC2A2 gene were identified, with six being novel, among which one was recurrent: c.1217T > G (p.L406R) (allele frequency: 4/22, 18%). Patients with biallelic missense variants showed milder metabolic acidosis than those with null variants. Two of five patients from nonconsanguineous families with rare homozygous variations showed 5.3 Mb and 36.6 Mb of homozygosity surrounding the variants, respectively; a region of homozygosity (ROH) involving the entire chromosome 3 covering the SLC2A2 gene, suggesting uniparental disomy 3, was detected in one patient.

CONCLUSIONS

Early diagnosis of FBS is difficult due to the heterogeneity of initial symptoms. Although short stature is a major issue of treatment for FBS, rhGH is not recommended in FBS patients who have normal GH stimulation tests. Patients with biallelic null variants may require alkali supplementation since urine bicarbonate loss is genetically related. ROH is a mechanism for rare homozygous variants of FBS in nonconsanguineous families.

Growth disorders caused by variants in epigenetic regulators: progress and prospects

Epigenetic modifications play an important role in regulation of transcription and gene expression. The molecular machinery governing epigenetic modifications, also known as epigenetic regulators, include non-coding RNA, chromatin remodelers, and enzymes or proteins responsible for binding, reading, writing and erasing DNA and histone modifications. Recent advancement in human genetics and high throughput sequencing technology have allowed the identification of causative variants, many of which are epigenetic regulators, for a wide variety of childhood growth disorders that include skeletal dysplasias, idiopathic short stature, and generalized overgrowth syndromes. In this review, we highlight the connection between epigenetic modifications, genetic variants in epigenetic regulators and childhood growth disorders being established over the past decade, discuss their insights into skeletal biology, and the potential of epidrugs as a new type of therapeutic intervention.

Clinical-genetic analysis of selected genes involved in the development of the human skeleton in 128 Czech patients with suspected congenital skeletal abnormalities

BACKGROUND

Congenital skeletal abnormalities are a heterogeneous group of diseases most commonly associated with small or disproportionate growth, cranial and facial dysmorphisms, delayed bone maturation, etc. Nonetheless, no detailed genotype-phenotype correlation in patients with specific genetic variants is readily available. Ergo, this study focuses on the analysis of patient phenotypes with candidate variants in genes involved in bone growth as detected by molecular genetic analysis.

METHODS

In this study we used molecular genetic methods to analyse the ACAN, COL2A1, FGFR3, IGFALS, IGF1, IGF1R, GHR, NPR2, STAT5B and SHOX genes in 128 Czech children with suspected congenital skeletal abnormalities. Pathogenic variants and variants of unclear clinical significance were identified and we compared their frequency in this study cohort to the European non-Finnish population. Furthermore, a prediction tool was utilised to determine their possible impact on the final protein. All clinical patient data was obtained during pre-test genetic counselling.

RESULTS

Pathogenic variants were identified in the FGFR3, GHR, COL2A1 and SHOX genes in a total of six patients. Furthermore, we identified 23 variants with unclear clinical significance and high allelic frequency in this cohort of patients with skeletal abnormalities. Five of them have not yet been reported in the scientific literature.

CONCLUSION

Congenital skeletal abnormalities may lead to a number of musculoskeletal, neurological, cardiovascular problems. Knowledge of specific pathogenic variants may help us in therapeutic procedures.

Parents' Knowledge and Perception Toward Short Stature in Saudi Arabia

Introduction Short stature is a common reason for referral to pediatric endocrinologists. A Saudi study highlights significant short stature prevalence, with parents exhibiting varied knowledge levels. Common normal variants of short stature are familial short stature, constitutional, and idiopathic short stature. Pathologic causes of short stature include growth hormone deficiency, genetic disorders, and chronic diseases. Parents' knowledge plays an important role in the diagnosis and early intervention of this condition. Insufficient studies prompt the authors to conduct a novel survey assessing Saudi parents' knowledge and perceptions of short stature, filling a research gap. Methodology This is a cross-sectional study conducted among Saudi Parents in five different regions of Saudi Arabia. A self-administered questionnaire was distributed among parents via an online survey. The questionnaire includes sociodemographic characteristics and questions to assess the knowledge and perception regarding short stature. Non-probability sampling targets parents living in Saudi Arabia. Data is analyzed by SPSS version 29 (IBM Inc., Armonk, New York). Results Our study on Saudi parents' knowledge of short stature reveals diverse awareness levels. While genetic causes are widely recognized in (71.6%; N=245) of parents (N=352), awareness drops for factors like low birth weight (23.9%; N=82) total of (N=352). Parents show uncertainty in recognizing short stature (51.4%; N=352) and varied beliefs on growth cessation. A majority (65.6%; N=231) of parents (N=352) prefer early intervention, with 41.5% (N=146) of parents (N=352) recognizing growth hormone therapy. Sociodemographic factors influence knowledge scores, with higher scores in males (21.03) and Central region residents (22.03; p<0.001). Notably, 83.4% (N=248) of parents (N=352) acknowledge psychological complications.  Conclusion Our study highlights varied awareness among parents regarding short stature, emphasizing genetic causes but demonstrating gaps in recognizing certain factors. Sociodemographic factors significantly influence knowledge scores. Psychological complications are widely acknowledged.

Micromechanical Loading Studies in Ex Vivo Cultured Embryonic Rat Bones Enabled by a Newly Developed Portable Loading Device

Mechanical loading has been described as having the potential to affect bone growth. In order to experimentally study the potential clinical applications of mechanical loading as a novel treatment to locally modulate bone growth, there is a need to develop a portable mechanical loading device enabling studies in small bones. Existing devices are bulky and challenging to transfer within and between laboratories and animal facilities, and they do not offer user-friendly mechanical testing across both ex vivo cultured small bones and in vivo animal models. To address this, we developed a portable loading device comprised of a linear actuator fixed within a stainless-steel frame equipped with suitable structures and interfaces. The actuator, along with the supplied control system, can achieve high-precision force control within the desired force and frequency range, allowing various load application scenarios. To validate the functionality of this new device, proof-of-concept studies were performed in ex vivo cultured rat bones of varying sizes. First, very small fetal metatarsal bones were microdissected and exposed to 0.4 N loading applied at 0.77 Hz for 30 s. When bone lengths were measured after 5 days in culture, loaded bones had grown less than unloaded controls (p < 0.05). Next, fetal rat femur bones were periodically exposed to 0.4 N loading at 0.77 Hz while being cultured ex vivo for 12 days. Interestingly, this loading regimen had the opposite effect on bone growth, i.e., loaded femur bones grew significantly more than unloaded controls (p < 0.001). These findings suggest that complex relationships between longitudinal bone growth and mechanical loading can be determined using this device. We conclude that our new portable mechanical loading device allows experimental studies in small bones of varying sizes, which may facilitate further preclinical studies exploring the potential clinical applications of mechanical loading.

Identification and analysis of individuals who deviate from their genetically-predicted phenotype

Findings from genome-wide association studies have facilitated the generation of genetic predictors for many common human phenotypes. Stratifying individuals misaligned to a genetic predictor based on common variants may be important for follow-up studies that aim to identify alternative causal factors. Using genome-wide imputed genetic data, we aimed to classify 158,951 unrelated individuals from the UK Biobank as either concordant or deviating from two well-measured phenotypes. We first applied our methods to standing height: our primary analysis classified 244 individuals (0.15%) as misaligned to their genetically predicted height. We show that these individuals are enriched for self-reporting being shorter or taller than average at age 10, diagnosed congenital malformations, and rare loss-of-function variants in genes previously catalogued as causal for growth disorders. Secondly, we apply our methods to LDL cholesterol (LDL-C). We classified 156 (0.12%) individuals as misaligned to their genetically predicted LDL-C and show that these individuals were enriched for both clinically actionable cardiovascular risk factors and rare genetic variants in genes previously shown to be involved in metabolic processes. Individuals whose LDL-C was higher than expected based on the genetic predictor were also at higher risk of developing coronary artery disease and type-two diabetes, even after adjustment for measured LDL-C, BMI and age, suggesting upward deviation from genetically predicted LDL-C is indicative of generally poor health. Our results remained broadly consistent when performing sensitivity analysis based on a variety of parametric and non-parametric methods to define individuals deviating from polygenic expectation. Our analyses demonstrate the potential importance of quantitatively identifying individuals for further follow-up based on deviation from genetic predictions.

Identification and analysis of individuals who deviate from their genetically-predicted phenotype

Findings from genome-wide association studies have facilitated the generation of genetic predictors for many common human phenotypes. Stratifying individuals misaligned to a genetic predictor based on common variants may be important for follow-up studies that aim to identify alternative causal factors. Using genome-wide imputed genetic data, we aimed to classify 158,951 unrelated individuals from the UK Biobank as either concordant or deviating from two well-measured phenotypes. We first applied our methods to standing height: our primary analysis classified 244 individuals (0.15%) as misaligned to their genetically predicted height. We show that these individuals are enriched for self-reporting being shorter or taller than average at age 10, diagnosed congenital malformations, and rare loss-of-function variants in genes previously catalogued as causal for growth disorders. Secondly, we apply our methods to LDL cholesterol. We classified 156 (0.12%) individuals as misaligned to their genetically predicted LDL cholesterol and show that these individuals were enriched for both clinically actionable cardiovascular risk factors and rare genetic variants in genes previously shown to be involved in metabolic processes. Individuals whose LDL-C was higher than expected based on the genetic predictor were also at higher risk of developing coronary artery disease and type-two diabetes, even after adjustment for measured LDL-C, BMI and age, suggesting upward deviation from genetically predicted LDL-C is indicative of generally poor health. Our results remained broadly consistent when performing sensitivity analysis based on a variety of parametric and non-parametric methods to define individuals deviating from polygenic expectation. Our analyses demonstrate the potential importance of quantitatively identifying individuals for further follow-up based on deviation from genetic predictions.

Author Summary

Human genetics is becoming increasingly useful to help predict human traits across a population owing to findings from large-scale genetic association studies and advances in the power of genetic predictors. This provides an opportunity to potentially identify individuals that deviate from genetic predictions for a common phenotype under investigation. For example, an individual may be genetically predicted to be tall, but be shorter than expected. It is potentially important to identify individuals who deviate from genetic predictions as this can facilitate further follow-up to assess likely causes. Using 158,951 unrelated individuals from the UK Biobank, with height and LDL cholesterol, as exemplar traits, we demonstrate that approximately 0.15% & 0.12% of individuals deviate from their genetically predicted phenotypes respectively. We observed these individuals to be enriched for a range of rare clinical diagnoses, as well as rare genetic factors that may be causal. Our analyses also demonstrate several methods for detecting individuals who deviate from genetic predictions that can be applied to a range of continuous human phenotypes.

Case report: A novel heterozygous frameshift mutation of ACAN in a Chinese family with short stature and advanced bone age

Short stature (OMIM: 165800) is a common pediatric disorder. Any abnormality in the cartilage formation of the growth plate can cause short stature. Aggrecan, encoded by ACAN, is an important component of the extracellular matrix. Mutations in ACAN have been reported to cause short stature. In the present study, we enrolled a Chinese family with short stature and advanced bone age across three generations. Whole-exome sequencing (WES) was performed on the proband to detect the candidate genes causing short stature in family. A novel heterozygous frameshift mutation (NM_013227.3:c.7230delT; NP_001356197.1: p. Phe2410Leufs*9) of the ACAN gene was confirmed to be a genetic lesion in this family. This variant, which was located in a functional site globular 3 (G3) domain of ACAN and predicted to be deleterious by informatics programs, was co-segregated with the affected family members by performing Sanger sequencing. Literatures review of growth hormone (GH) treatment outcome of all previously reported ACAN patients suggesting that the G3 domain of ACAN may be critical in the development of short stature and growth hormone treatment. These findings not only contribute to the genetic diagnosis and counseling of the family, but will also expand the mutation spectrum of ACAN.

SHOX Deletion and Idiopathic Short Stature: What Does the Clinician Need to Know? Case Series Report

Children diagnosticated with idiopathic short stature (ISS) are probably, in most cases, underdiagnosticated. The genetic causes of ISS may be mutations of genes involved in local regulation of the growth plate or genes involved in the GH-IGF1 axis physiology. We present a kindred of five children evaluated for short stature or low normal stature, initially diagnosticated as idiopathic short stature, familial short stature, or being small for gestational age. Clinical signs suggestive of SHOX deletion screening in a child with short stature are low arm span/height ratio, increased sitting height/height ratio, BMI > 50% percentile, Madelung deformity, cubitus valgus, bowing and shortening of the forearm, dislocation of the ulna (at the elbow), and the appearance of muscular hypertrophy. Radiological characteristics suggestive of SHOX deficiency are triangularisation of the distal radial epiphysis, an enlarged diaphysis of the radius plus bowing of the radius, the convexity of the distal radial metaphysis, short fourth and fifth metacarpals, pyramidalization of the carpal row. Treatment with rGH is approved for children with SHOX gene deficiency and short stature. This kindred is an example that familial short stature, idiopathic short stature, and short stature due to a small gestational age are not final diagnoses. Complex investigations are necessary to identify the precise cause, leading to optimal clinical management. Treatment with rGH is an option for some of them; for others, it has no therapeutic response and, in some cases, is even harmful.

Cytogenomic Characterization of a Novel de novo Balanced Reciprocal Translocation t(1;12) by Genome Sequencing Leading to Fusion Gene Formation of EYA3/EFCAB4b

Introduction

The accurate detection of breakpoint regions of disease-associated chromosomal rearrangements helps understand the molecular mechanisms and identify the risks involved with disrupted genes.

Methods

In this study, a girl with growth retardation is characterized using positional cloning and genome sequencing. The techniques include fluorescence in situ hybridization (FISH) with paint (WCP) and bacterial-artificial chromosomes (BAC) probes, PCR, real-time PCR, and short and long-read sequencing.

Results

The translocation was identified by GTG banding and confirmed by WCP FISH. Microarray ruled out the involvement of other copy number variations except for 6 homozygous regions which are not disease-causing variants. Fine mapping with FISH showed split signals with BAC clone RP11-312A3. Genome sequencing of short-read with an average 30× depth and long-read sequencing technology with a 3.8× coverage identified both breakpoints, confirmed by Sanger sequencing, that showed microhomology. The breakpoint at 1p and 12p regions disrupted EYA3 and EFCAB4B genes. Expression analysis of EYA3 showed a 7-fold increase, suggesting the formation of a fusion gene with EFCAB4B. EYA3 is involved in skeleton development, and EFCAB4B plays a role in calcium metabolism, which may be relevant for the patient's phenotype.

Conclusion

The systematic application of genome techniques to translocations and their advantages is discussed.

A Genetic Approach in the Evaluation of Short Stature

Short stature is considered a condition in which the height is 2 standard deviations below the mean height of a given age, sex, and population group. Human height is a polygenic and heterogeneous characteristic, and its heritability is reported to be approximately 80%. More than 600 variants associated with human growth were detected in the genome-wide association studies. Rare and common variants concurrently affect human height. The rare variations that play a role in human height determination and have a strong impact on protein functions lead to monogenic short stature phenotypes, which are a highly heterogeneous group. With rapidly developing technologies in the last decade, molecular genetic tests have begun to be used widely in clinical genetics, and thus, the genetic etiology of several rare diseases has been elucidated. Identifying the genetic etiology underlying idiopathic short stature which represents phenotypically heterogeneous group of diseases ranging from isolated short stature to severe and syndromic short stature has promoted the understanding of the genetic regulation of growth plate and longitudinal bone growth. In cases of short stature, definite molecular diagnosis based on genetic evaluation enables the patient and family to receive genetic counseling on the natural course of the disease, prognosis, genetic basis, and recurrence risk. The determination of the genetic etiology in growth disorders is essential for the development of novel targeted therapies and crucial in the development of mutation-specific treatments in the future.

Metabolomic Differential Compounds Reflecting the Clinical Efficacy of Polyethylene Glycol Recombinant Human Growth Hormone in the Treatment of Childhood Growth Hormone Deficiency

Understanding metabolite profiles may aid in providing a reference for individualized treatment using PEG-rhGH. Therefore, this study aimed to evaluate the clinical efficacy of PEG-rhGH in treating GHD patients by using a metabolomic approach. Fifty-seven pediatric participants treated with PEG-rhGH were enrolled (28 GHD patients with high clinical efficacy and 29 GHD patients with lower clinical efficacy). Serum samples from all patients were first collected at baseline for biochemical detection; then metabolite levels were measured using gas chromatography time-of-flight mass spectrometry. The candidates included heptadecanoic acid, stearic acid, 2-hydroxybutyric acid, myristic acid, palmitoleic acid, D-galactose, dodecanoic acid, and oleic acid. The related metabolic pathways involved fatty acid metabolism and energy metabolism. This study suggested that growth gains of PEG-rhGH treatment might be differentiated by altered serum levels of fatty acid. Collectively, the metabolomic study provides unique insights into the use of PEG-rhGH as a therapeutic strategy for individualized treatment.

Invaluable Role of Consanguinity in Providing Insight into Paediatric Endocrine Conditions: Lessons Learnt from Congenital Hyperinsulinism, Monogenic Diabetes, and Short Stature

Consanguineous families have often played a role in the discovery of novel genes, especially in paediatric endocrinology. At this time, it has been estimated that over 8.5% of all children worldwide have consanguineous parents. Consanguinity is linked to demographic, cultural, and religious practises and is more common in some areas around the world than others. In children with endocrine conditions from consanguineous families, there is a greater probability that a single-gene condition with autosomal recessive inheritance is causative. From 1966 and the first description of Laron syndrome, through the discovery of the first KATP channel genes ABCC8 and KCNJ11 causing congenital hyperinsulinism (CHI) in the 1990s, to recent discoveries of mutations in YIPF5 as the first cause of monogenic diabetes due to the disruption of the endoplasmic reticulum (ER)-to-Golgi trafficking in the β-cell and increased ER stress; positive genetic findings in children from consanguinity have been important in elucidating novel genes and mechanisms of disease, thereby expanding knowledge into disease pathophysiology. The aim of this narrative review was to shed light on the lessons learned from consanguineous pedigrees with the help of 3 fundamental endocrine conditions that represent an evolving spectrum of pathophysiological complexity - from CHI, a typically single-cell condition, to monogenic diabetes which presents with uniform biochemical parameters (hyperglycaemia and glycosuria), despite varying aetiologies, up to the genetic regulation of human growth - the most complex developmental phenomenon.

Altered DNA methylation at age-associated CpG sites in children with growth disorders: impact on age estimation?

Age estimation based on DNA methylation (DNAm) can be applied to children, adolescents and adults, but many CG dinucleotides (CpGs) exhibit different kinetics of age-associated DNAm across these age ranges. Furthermore, it is still unclear how growth disorders impact epigenetic age predictions, and this may be particularly relevant for a forensic application. In this study, we analyzed buccal mucosa samples from 95 healthy children and 104 children with different growth disorders. DNAm was analysed by pyrosequencing for 22 CpGs in the genes PDE4C, ELOVL2, RPA2, EDARADD and DDO. The relationship between DNAm and age in healthy children was tested by Spearman’s rank correlation. Differences in DNAm between the groups “healthy children” and the (sub-)groups of children with growth disorders were tested by ANCOVA. Models for age estimation were trained (1) based on the data from 11 CpGs with a close correlation between DNAm and age (R ≥ 0.75) and (2) on five CpGs that also did not present significant differences in DNAm between healthy and diseased children. Statistical analysis revealed significant differences between the healthy group and the group with growth disorders (11 CpGs), the subgroup with a short stature (12 CpGs) and the non-short stature subgroup (three CpGs). The results are in line with the assumption of an epigenetic regulation of height-influencing genes. Age predictors trained on 11 CpGs with high correlations between DNAm and age revealed higher mean absolute errors (MAEs) in the group of growth disorders (mean MAE 2.21 years versus MAE 1.79 in the healthy group) as well as in the short stature (sub-)groups; furthermore, there was a clear tendency for overestimation of ages in all growth disorder groups (mean age deviations: total growth disorder group 1.85 years, short stature group 1.99 years). Age estimates on samples from children with growth disorders were more precise when using a model containing only the five CpGs that did not present significant differences in DNAm between healthy and diseased children (mean age deviations: total growth disorder group 1.45 years, short stature group 1.66 years). The results suggest that CpGs in genes involved in processes relevant for growth and development should be avoided in age prediction models for children since they may be sensitive for alterations in the DNAm pattern in cases of growth disorders.

Arm Span and Its Relation to Height in a 2- to 17-Year-Old Reference Population and Heterozygous Carriers of ACAN Variants

BACKGROUND/OBJECTIVES

In the clinical assessment of a short or tall child, estimating body disproportion is useful to assess the likelihood of a primary growth disorder, e.g., skeletal dysplasia. Our objectives were (1) to use data from the Maastricht study on healthy children (2-17 years) to calculate relative arm span (AS) for height (H) to serve as age references for clinical purposes; (2) to assess its age and sex dependency; and (3) to investigate relative AS adjustment for age and sex in individuals with ACAN haploinsufficiency.

METHODS

The Maastricht study data (2,595 Caucasian children, 52% boys, 48% girls) were re-analysed to produce reference tables and graphs for age and sex of AS - H and AS/H. Published information on AS/H in Europeans was used as reference data for adults. Relative AS from 33 patients with ACAN haploinsufficiency were plotted against reference data and expressed as standard deviation score (SDS) for age and sex.

RESULTS

Mean AS - H from 2 to 17 years increased from -1.2 to +1.5 cm in boys and from -4.8 to +1.6 cm in girls. Mean AS/H increased from 0.9848 to 1.0155 in boys and from 0.9468 to 1.0028 in girls. Mean AS/H in patients with ACAN haploinsufficiency was approximately 1.0, 1.5 and 0.5 SDS in young children, adolescents and 20- to 50-year-olds, respectively, and normal thereafter.

CONCLUSIONS

These reference charts can be used for 2- to 17-year-old children/adolescents. Carriers of ACAN haploinsufficiency have an elevated mean AS/H in childhood and adolescence and a slightly elevated ratio till 50 years.

The effect of treatment with recombinant human growth hormone (rhGH) on linear growth and adult height in children with idiopathic short stature (ISS): a systematic review and meta-analysis

OBJECTIVES

Idiopathic short stature (ISS) is a recognized, albeit a controversial indication for treatment with recombinant human growth hormone (rhGH).The objective of the present study was to conduct a systematic review of the literature and meta-analyses of selected studies about the use of rhGH in children with ISS on linear growth and adult height (AH).

METHODS

A systematic literature search was conducted to identify relevant studies published till February 28, 2017 in the following databases: Medline (PubMed), Scopus and Cochrane Central Registry of Controlled Trials. After exclusion of duplicate studies, 3,609 studies were initially identified. Of those, 3,497 studies were excluded during the process of assessing the title and/or the abstract. The remaining 112 studies were evaluated further by assessing the full text; 21 of them fulfilled all the criteria in order to be included in the current meta-analysis.

RESULTS

Children who received rhGH had significantly higher height increment at the end of the first year, an effect that persisted in the second year of treatment and achieved significantly higher AH than the control group. The difference between the two groups was equal to 5.3 cm (95% CI: 3.4-7 cm) for male and 4.7 cm (95% CI: 3.1-6.3 cm) for female patients.

CONCLUSION

In children with ISS, treatment with rhGH improves short-term linear growth and increases AH compared with control subjects. However, the final decision should be made on an individual basis, following detailed diagnostic evaluation and careful consideration of both risks and benefits of rhGH administration.

Longitudinal Bone Growth Stimulating Effect of Allium macrostemon in Adolescent Female Rats

Allium macrostemon (AM) may affect bone growth by regulating bone formation and resorption. To examine the effect of AM on bone growth, 48 rats were divided into four administration groups in which either distilled water, AM (100 and 300 mg/kg), or recombinant human growth hormone (rhGH; 20 μg/kg) was administered for 10 days. On day 9, all animals were intraperitoneally injected with tetracycline hydrochloride (20 mg/kg), and 48 h after the injection, the rats were sacrificed. Their tibial sections were photographed to measure bone growth. Antigen-specific immunohistochemistry was performed to detect insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein-2 (BMP-2). The food intake of the AM 100 mg/kg group was higher; however, the food intake of the AM 300 mg/kg group was less than that of the control group. The rhGH and AM 100 mg/kg groups showed greater rates of bone growth (359.0 ± 23.7 and 373.1 ± 28.0 μm/day, respectively) compared with the control group. IGF-1 and BMP-2 in the AM and rhGH groups were highly expressed. Indigestion at higher doses of AM led to nonsignificant bone growth in spite of increased IGF-1 and BMP-2 expression. Therefore, a suitable amount of AM could increase bone growth.

A new approach to the diagnosis of short stature

Growth is the task of children. We review the normal process of linear growth from the fetus through adolescence and note that growth is the result of age- and gender-dependent interactions among key genetic, environmental, dietary, socioeconomic, developmental, behavioral, nutritional, metabolic, biochemical, and hormonal factors. We then define the wide range of normative data at each stage of growth and note that a pattern within this range is generally indicative of good general health and that growth significantly slower than this range may lead to growth faltering and subsequent short stature. Although not often emphasized, we detail how to properly measure infants and children because height velocity is usually determined from two height measurements (both relatively large values) to calculate the actual height velocity (a relatively much smaller number in comparison). Traditionally the physiology of growth has been taught from an endocrine-centric point-of-view. Here we review the hypothalamic-pituitary-end organ axes for the GH/IGF-1 and gonadal steroid hormones (hypothalamic-pituitary-gonadal axis), both during "mini"-puberty as well as at puberty. However, over the past few decades much more emphasis has been placed on the growth plate and its many interactions with the endocrine system but also with its own intrinsic physiology and gene mutations. These latter, whether individually (large effect size) or in combination with many others including endocrine system-based, may account in toto for meaningful differences in adult height. The clinical assessment of children with short stature includes medical, social and family history, physical exam and importantly proper interpretation of the growth curve. This analysis should lead to judicious use of screening laboratory and imaging tests depending on the pre-test probability (Bayesian inference) of a particular diagnosis in that child. In particular for those with no pathological features in the history and physical exam and a low, but normal height velocity, may lead only to a bone age exam and reevaluation (re-measurement), perhaps 6 months later. he next step depends on the comfort level of the primary care physician, the patient, and the parent; that is, whether to continue with the evaluation with more directed, more sophisticated testing, again based on Bayesian inference or to seek consultation with a subspecialist pediatrician based on the data obtained. This is not necessarily an endocrinologist. The newest area and the one most in flux is the role for genetic testing, given that growth is a complex process with large effect size for single genes but smaller effect sizes for multiple other genes which in the aggregate may be relevant to attained adult height. Genetics is a discipline that is rapidly changing, especially as the cost of exome or whole gene sequencing diminishes sharply. Within a decade it is quite likely that a genetic approach to the evaluation of children with short stature will become the standard, truncating the diagnostic odyssey and be cost effective as fewer biochemical and imaging studies are required to make a proper diagnosis.

Relationship between the short stature and the prevalence of metabolic syndrome and insulin resistance markers in workers of a private educational institution in Peru

BACKGROUND AND AIMS

Short stature has been linked with the development of metabolic syndrome (MetS). However, only one study has been conducted in Latin American adults. We aimed to assess the association between short stature and MetS in workers of a private educational institution in Peru. In addition, we evaluated the association between height and surrogate markers of insulin resistance (IR).

METHODS

We performed an analytical cross-sectional study. We categorized the height in tertiles and evaluated MetS according to the Latin American Diabetes Association statement. We used the triglycerides and glucose (TyG) index and the triglycerides to HDL-cholesterol (TG/HDL-c) ratio as IR markers. We elaborated crude and adjusted Poisson generalized linear models to evaluate the association between height tertiles and MetS. For the IR markers, we carried out crude and adjusted linear regressions.

RESULTS

We analyzed 1080 participants and the overall prevalence of MetS was 16.2%. In the adjusted Poisson generalized linear model, using the high tertile as a reference, we found statistically significant differences in the prevalence of MetS with the low and intermediate tertile (aPR = 2.03; 95%CI: 1.48-2.77 and aPR = 1.41; 95%CI: 1.01-1.99; respectively). In the gender-stratified analysis, we found statistical significance between height and MetS when comparing high and low tertile for both genders. For IR markers, we found an inverse association between the height and TyG index (aβ = -0.14; 95%CI: 0.19 to -0.10) and TG/HDL-c ratio (aβ = -0.62; 95%CI: 0.84 to -0.39). When we stratified by gender, the association for both secondary outcomes and height remained statistically significant in both groups.

CONCLUSIONS

We found an association between short stature and the prevalence of MetS and IR markers. We need studies with national representative samples to define the threshold of short stature with better sensitivity and specificity for the screening of MetS.

Whole-exome sequencing identified a novel variant in an Iranian patient affected by pycnodysostosis

BACKGROUND

Whole-exome sequencing (WES) has emerged as a successful diagnostic tool in molecular genetics laboratories worldwide. In this study, we aimed to find the potential genetic cause of skeletal disease, a heterogeneous disease, revealing the obvious short stature phenotype. In an Iranian family, we used solo-WES in a suspected patient to decipher the potential genetic cause(s).

METHODS

A comprehensive clinical and genotyping examination was applied to suspect the disease of the patient. The solo clinical WES was exploited, and the derived data were filtered according to the standard pipelines. In order to validate the WES finding, the region harboring the candidate variant in the CTSK gene was amplified from genomic DNA and sequenced directly by Sanger sequencing.

RESULTS

Sequence analysis revealed a rare novel nonsense variant, p.(Trp320*); c.905G>A, in the CTSK gene (NM_000396.3). In silico analysis shed light on the contribution of the variant to the pathogenicity of pycnodysostosis. This variant was confirmed by Sanger sequencing and further clinical examinations of the patient confirmed the disease.

CONCLUSION

The present study shows a rare variant of the CTSK gene, which inherited as autosomal recessive, in an Iranian male patient with pycnodysostosis. Taken together, the novel nonsense CTSK variant meets the criteria of being likely pathogenic according to the American College of Medical Genetics and Genomics-the Association for Molecular Pathology (ACMG-AMP) variant interpretation guidelines.

Genetic regulation of linear growth

Linear growth occurs at the growth plate. Therefore, genetic defects that interfere with the normal function of the growth plate can cause linear growth disorders. Many genetic causes of growth disorders have already been identified in humans. However, recent genome-wide approaches have broadened our knowledge of the mechanisms of linear growth, not only providing novel monogenic causes of growth disorders but also revealing single nucleotide polymorphisms in genes that affect height in the general population. The genes identified as causative of linear growth disorders are heterogeneous, playing a role in various growth-regulating mechanisms including those involving the extracellular matrix, intracellular signaling, paracrine signaling, endocrine signaling, and epigenetic regulation. Understanding the underlying genetic defects in linear growth is important for clinicians and researchers in order to provide proper diagnoses, management, and genetic counseling, as well as to develop better treatment approaches for children with growth disorders.

Growth hormone therapy in children; research and practice - A review

Short stature remains the most common reason for referral to a pediatric Endocrinologist and its management remains a challenge. One of the main controversies is the diagnosis of idiopathic short stature and the role of new technologies for genetic investigation of children with inadequate growth. Complexities in management of children with short stature includes selection of who should receive interventions such as recombinant human growth hormone, and how should this agent dose be adjusted during treatment. Should anthropometrical data be the primary determinant or should biochemical and genetic data be used to improve growth response and safety? Furthermore, what is considered a suboptimal response to growth hormone therapy and how should this be managed? Treatment of children with short stature remains a "hot" topic and more data is needed in several areas. These issues are reviewed in this paper.

The causes and consequences of pituitary gigantism

In the general population, height is determined by a complex interplay between genetic and environmental factors. Pituitary gigantism is a rare but very important subgroup of patients with excessive height, as it has an identifiable and clinically treatable cause. The disease is caused by chronic growth hormone and insulin-like growth factor 1 secretion from a pituitary somatotrope adenoma that forms before the closure of the epiphyses. If not controlled effectively, this hormonal hypersecretion could lead to extremely elevated final adult height. The past 10 years have seen marked advances in the understanding of pituitary gigantism, including the identification of genetic causes in ~50% of cases, such as mutations in the AIP gene or chromosome Xq26.3 duplications in X-linked acrogigantism syndrome. Pituitary gigantism has a male preponderance, and patients usually have large pituitary adenomas. The large tumour size, together with the young age of patients and frequent resistance to medical therapy, makes the management of pituitary gigantism complex. Early diagnosis and rapid referral for effective therapy appear to improve outcomes in patients with pituitary gigantism; therefore, a high level of clinical suspicion and efficient use of diagnostic resources is key to controlling overgrowth and preventing patients from reaching very elevated final adult heights.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

New developments in the genetic diagnosis of short stature

PURPOSE OF REVIEW

Genome-wide approaches including genome-wide association studies as well as exome and genome sequencing represent powerful new approaches that have improved our ability to identify genetic causes of human disorders. The purpose of this review is to describe recent advances in the genetic causes of short stature.

RECENT FINDINGS

In addition to SHOX deficiency which is one of the most common causes of isolated short stature, PAPPA2, ACAN, NPPC, NPR2, PTPN11 (and other rasopathies), FBN1, IHH and BMP2 have been identified in isolated growth disorders with or without other mild skeletal findings. In addition, novel genetic causes of syndromic short stature have been discovered, including pathogenic variants in BRCA1, DONSON, AMMECR1, NFIX, SLC25A24, and FN1.

SUMMARY

Isolated growth disorders are often monogenic. Specific genetic causes typically have specific biochemical and/or phenotype characteristics which are diagnostically helpful. Identification of additional subjects with a specific genetic cause of short stature often leads to a broadening of the known clinical spectrum for that condition. The identification of novel genetic causes of short stature has provided important insights into the underlying molecular mechanisms of growth failure.

Monoallelic BMP2 Variants Predicted to Result in Haploinsufficiency Cause Craniofacial, Skeletal, and Cardiac Features Overlapping Those of 20p12 Deletions

Bone morphogenetic protein 2 (BMP2) in chromosomal region 20p12 belongs to a gene superfamily encoding TGF-β-signaling proteins involved in bone and cartilage biology. Monoallelic deletions of 20p12 are variably associated with cleft palate, short stature, and developmental delay. Here, we report a cranioskeletal phenotype due to monoallelic truncating and frameshift BMP2 variants and deletions in 12 individuals from eight unrelated families that share features of short stature, a recognizable craniofacial gestalt, skeletal anomalies, and congenital heart disease. De novo occurrence and autosomal-dominant inheritance of variants, including paternal mosaicism in two affected sisters who inherited a BMP2 splice-altering variant, were observed across all reported families. Additionally, we observed similarity to the human phenotype of short stature and skeletal anomalies in a heterozygous Bmp2-knockout mouse model, suggesting that haploinsufficiency of BMP2 could be the primary phenotypic determinant in individuals with predicted truncating variants and deletions encompassing BMP2. These findings demonstrate the important role of BMP2 in human craniofacial, skeletal, and cardiac development and confirm that individuals heterozygous for BMP2 truncating sequence variants or deletions display a consistent distinct phenotype characterized by short stature and skeletal and cardiac anomalies without neurological deficits.