Prevalence of SHOX haploinsufficiency among short statured children

Tackling access and payer barriers for growth hormone therapy in Saudi Arabia: a consensus statement for the Saudi Working Group for Pediatric Endocrinology

Prompt diagnosis and early treatment are key goals to optimize the outcomes of children with growth hormone deficiency (GHD) and attain the genetically expected adult height. Nonetheless, several barriers can hinder prompt diagnosis and treatment of GHD, including payer-related issues. In Saudi Arabia, moderate-to-severe short stature was reported in 13.1 and 11.7 % of healthy boys and girls, respectively. Several access and payer barriers can face pediatric endocrinologists during the diagnosis and treatment of GHD in Saudi Arabia. Insurance coverage policies can restrict access to diagnostic tests for GHD and recombinant human growth hormone (rhGH) due to their high costs and lack of gold-standard criteria. Some insurance policies may limit the duration of treatment with rhGH or the amount of medication covered per month. This consensus article gathered the insights of pediatric endocrinologists from Saudi Arabia to reflect the access and payer barriers to the diagnostic tests and treatment options of children with short stature. We also discussed the current payer-related challenges endocrinologists face during the investigations of children with short stature. The consensus identified potential strategies to overcome these challenges and optimize patient management.

Genetic analysis, ultrasound phenotype, and pregnancy outcomes of fetuses with Xp22.33 or Yp11.32 microdeletions

OBJECTIVES

The phenotypes of Xp22.33 or Yp11.32 microdeletions comprising the short-stature homeobox (SHOX) gene have been extensively described in adults and children. Herein, the prenatal ultrasound phenotype and pregnancy outcomes of fetuses with Xp22.33/Yp11.32 microdeletions were analyzed to improve our understanding, diagnosis, and monitoring of this genetic condition in the fetal stage.

METHODS

A total of 9,100 pregnant women referred to tertiary units for prenatal diagnosis were evaluated by chromosomal microarray analysis(CMA).

RESULTS

Seven (0.08 %) fetuses had Xp22.33/Yp11.32 microdeletions, ranging from 243 kb to 1.1 Mb, that comprised SHOX. The ultrasonic phenotypes differed among these fetuses, with three fetuses presenting abnormal bone development, one had labial-palatal deformity and strawberry head, two had an abnormal ultrasonic soft marker, and one had no abnormalities. After genetic counseling, only one couple underwent pedigree assessment, which confirmed the paternal origin of the microdeletion. This infant presented delayed speech development, whereas other three infants showed a typical postnatal development. In three cases, the parents chose to terminate the pregnancy.

CONCLUSIONS

The ultrasonic phenotype of fetuses with Xp22.33/Yp11.32 microdeletions resulting in SHOX heterozygosity loss is variable. Prenatal CMA can quickly and effectively diagnose Xp22.33/Yp11.32 microdeletions and SHOX loss, which may help prenatal counseling.

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.

Clinical Indications for Growth Hormone Therapy

Growth hormone (GH) is an injectable medication originally used to replace the deficiency of the hormone, but has expanded to treating conditions that may reduce growth and adult height even when the body maintains endogenous GH production. In the United States, there are 8 Food and Drug Administration (FDA)-approved indications for pediatric GH therapy: GH deficiency, Prader-Willi Syndrome, small for gestational age (SGA) without catch-up growth, idiopathic short stature, Turner syndrome, SHOX gene haploinsufficiency, Noonan Syndrome, and chronic renal insufficiency. We characterize the growth patterns and effects of GH treatment in each of these indications. We also review patterns of growth that warrant referral to a pediatric endocrinologist, as well as safety updates. This review is intended to guide practitioners on the initial evaluation and management of patients with short stature, and the indications for GH therapy.

Detection of SHOX Gene Variations in Patients with Skeletal Abnormalities with or without Short Stature

OBJECTIVE

SHOX gene mutations constitute one of the genetic causes of short stature. The clinical phenotype includes variable degrees of growth impairment, such as Langer mesomelic dysplasia (LMD), Léri-Weill dyschondrosteosis (LWD) or idiopathic short stature (ISS). The aim of this study was to describe the clinical features and molecular results of SHOX deficiency in a group of Turkish patients who had skeletal findings with and without short stature.

METHODS

Forty-six patients with ISS, disproportionate short stature or skeletal findings without short stature from 35 different families were included. SHOX gene analysis was performed using Sanger sequencing and multiplex ligation-dependent probe amplification analysis.

RESULTS

Three different point mutations (two nonsense, one frameshift) and one whole SHOX gene deletion were detected in 15 patients from four different families. While 4/15 patients had LMD, the remaining patients had clinical features compatible with LWD. Madelung’s deformity, cubitus valgus, muscular hypertrophy and short forearm were the most common phenotypic features, as well as short stature. Additionally, hearing loss was detected in two patients with LMD.

CONCLUSION

This study has presented the clinical spectrum and molecular findings of 15 patients with SHOX gene mutations or deletions. SHOX deficiency should be especially considered in patients who have disproportionate short stature or forearm anomalies with or without short stature. Although most of the patients had partial or whole gene deletions, SHOX gene sequencing should be performed in suspected cases. Furthermore, conductive hearing loss may rarely accompany these clinical manifestations.

Novel Clinical Criteria Allow Detection of Short Stature Homeobox-Containing Gene Haploinsufficiency Caused by Either Gene or Enhancer Region Defects

INTRODUCTION

Short stature homeobox-containing gene (SHOX) haploinsufficiency is associated with short stature, Madelung deformity and mesomelia. Current clinical screening tools are based on patients with intragenic variants or deletions. However, recent discoveries showed that deletions of the enhancer elements are quite common. The majority of these patients show less body disproportion and respond better to recombinant human growth hormone treatment. We redefined clinical criteria for genetic analysis to facilitate detection of the full spectrum of SHOX haploinsufficiency.

METHODS

We analyzed 51 children with SHOX variants or deletions and 25 children with a deletion in its enhancer region. Data were compared to 277 children referred for suspicion of growth failure without endocrine or genetic pathology.

RESULTS

Only half of the patients with an enhancer region deletion fulfilled any of the current screening criteria. We propose new clinical criteria based on sitting height to height ratio >1 SDS or arm span ≥3 cm below height, with a sensitivity of 99%. When these criteria are combined with obligatory short stature, the sensitivity to detect SHOX haploinsufficiency is 68.1%, the specificity 80.6%, and the number needed to screen 21 patients.

CONCLUSION

Novel clinical criteria for screening for SHOX haploinsufficiency allow the detection of patients within the full genetic spectrum, that is, intragenic variants and enhancer region deletions.

Glucose Metabolism in Turner Syndrome

Turner syndrome (TS) is one of the most common female chromosomal disorders. The condition is caused by complete or partial loss of a single X chromosome. Adult patients with TS have a high prevalence of diabetes mellitus (DM). Deranged glucose metabolism in this population seems to be genetically triggered. The traditional risk factors for DM in the general population may not play a major role in the pathogenesis of DM in patients with TS. This review focuses on the latest research studies pertaining to abnormalities of glucose metabolism in TS. We extensively review the available evidence pertaining to the influence of insulin secretion and sensitivity, obesity, autoimmunity, lifestyle, growth hormone, and sex hormone replacement therapy on the occurrence of DM in these patients.

SHOX gene deletion screening by FISH in children with short stature and Madelung deformity and their characteristics

Background The short stature homeobox-containing (SHOX) gene strongly affects height. Therefore, a better understanding of SHOX haploinsufficiency could be advantageous to early diagnosis and treatment. We investigated the rate of SHOX haploinsufficiency in patients of short stature and documented their anthropometric measurements. Methods Between 2010 and 2017, we evaluated 86 patients (70 females, 16 males; age 4.3-18 years) with clinical diagnoses of short stature and Madelung deformity (MD). Clinical abnormalities are presented for patients with MD with and without SHOX haploinsufficiency as determined by fluorescence in situ hybridisation (FISH). Results According to our inclusion criteria, 78 of 86 patients (70 females, 16 males) had short stature (height <-2.5 standard deviation [SD]) and a family history suggestive of short stature. Eight patients had short stature, a family history suggestive of short stature and MD. MD was obvious in eight children in radiographic examinations. Although five of these had no deletion of SHOX, three had deletion of this gene. The deletion detection rate was 37.5% in the individuals with short stature and MD, i.e. Leri-Weill dyschondrosteosis syndrome (LWS), whilst no deletions were detected in the individuals with only short stature. One individual responded well to growth hormone (GH) treatment for the first 2 years but then developed an intolerance with persistently elevated insulin-like growth factor-1 (IGF-1) levels. Conclusions As we likely missed cases due to our methodology, the routine analysis for SHOX screening should be firstly multiplex ligation-dependent probe amplification (MLPA). The incidence of MD may have been higher in the cohort if X-rays were performed in all individuals. GH treatment was not well tolerated in one case due to persistently elevated IGF-1 levels, and long-term evaluations of patients with SHOX deficiency are required.

SHOX haploinsufficiency presenting with isolated short long bones in the second and third trimester

Haploinsufficiency of the transcription factor short stature homeobox (SHOX) manifests as a spectrum of clinical phenotypes, ranging from disproportionate short stature and Madelung deformity to isolated short stature. Here, we describe five infants with molecularly confirmed diagnoses of SHOX haploinsufficiency who presented in utero with short long bones during routine antenatal scanning from as early as 19 weeks gestation. Other foetal growth parameters were normal. The molecular basis of SHOX haploinsufficiency was distinct in each case. In four cases, SHOX haploinsufficiency was inherited from a previously undiagnosed parent. In our de novo case, SHOX haploinsufficiency reflected the formation of a derivative sex chromosome during paternal meiosis. Final adult height in the SHOX-deficient parents ranged from -1.9 to -1.2 SDS. All affected parents had disproportionately short limbs and two affected mothers had bilateral Madelung deformity. To our knowledge, SHOX haploinsufficiency has not previously been reported to present in utero. Our experience illustrates that SHOX deficiency should form part of the differential diagnosis of foetal short long bones and suggests a low threshold for genetic testing. This should be particularly targeted at, but not limited to, families with a history of features suggestive of SHOX deficiency. Data on the postnatal growth of our index cases is presented which demonstrates that antenatal presentation of SHOX haploinsufficiency is not indicative of severe postnatal growth restriction. Early identification of SHOX deficiency will enable accurate genetic counselling reflecting a good postnatal outcome and facilitate optimal initiation of growth hormone therapy.

Next generation sequencing-based mutation screening of 86 patients with idiopathic short stature

Although mutations in ACAN, FGFR3, NPR2, and SHOX typically lead to skeletal dysplasia, and mutations in GHRHR, GH1, GHR, STAT5B, IGF1, IGFALS, and IGF1R usually underlie hormonal defects of the growth hormone (GH)-insulin-like growth factor 1 (IGF1) axis, such mutations have also been identified in patients with idiopathic short stature (ISS). Of these, SHOX abnormalities are known to account for a certain percentage of ISS cases, whereas the frequency of mutations in the other 10 genes in ISS cohorts remains unknown. Here, we performed next-generation sequencing-based mutation screening of the 10 genes in 86 unrelated Japanese ISS patients without SHOX abnormalities. We searched for rare protein-altering variants. The functional significance of the identified variants was assessed by in silico analyses. Consequently, we identified 18 heterozygous rare variants in 19 patients, including four probable damaging variants in ACAN, six pathogenicity-unknown variants in FGFR3, GHRHR, GHR, and IGFALS, and eight possible benign variants. Pathogenic variants in NPR2, GH1, and IGF1 were absent from our cohort. Unlike previously reported patients with ACAN mutations, our four patients with ACAN variants manifested non-specific short stature with age-appropriate or mildly delayed bone ages, and had parents of normal stature. These results indicate that ACAN mutations can underlie ISS without characteristic skeletal features, and that such mutations are possibly associated with de novo occurrence or low penetrance. In addition, our data imply that mutations in FGFR3, NPR2, and GH-IGF1 axis genes play only limited roles in the etiology of ISS.

Short stature homeobox-containing gene duplications in 3.7% of girls with tall stature and normal karyotypes

AIM

The short stature homeobox-containing gene (SHOX) plays an important role in short stature, but has not been explored in detail in a tall stature population before. This study explored the prevalence of SHOX aberrations in girls diagnosed with idiopathic tall stature with a normal karyotype.

METHODS

We studied SHOX aberrations in 81 girls with a median age of 10.43 (7.17-12.73) years diagnosed with tall stature who were referred to our clinic at Copenhagen University Hospital, Denmark, between 2003 and 2013. SHOX copy variations were analysed by quantitative polymerase chain reaction, and aberrations were confirmed by multiplex ligation probe-dependent amplification.

RESULTS

One extra SHOX copy was found in three (3.7%) of the 81 girls with tall stature, and their heights were 2.87, 3.71 and 3.98 standard deviation scores (SDS) and above the median height SDS of the girls with two SHOX copies. Their sitting height/height ratios (-3.08, -2.00 and -2.18 SDS) were all lower than the population mean. Despite these SHOX duplications, the three girls were clinically and biochemically comparable to the 78 girls with two SHOX copies.

CONCLUSION

This study was the first to demonstrate SHOX duplications in three girls with tall stature and normal karyotypes.