Dyschondrosteosis Research Articles

Mild phenotypes in patients with different deletions in the 3' enhancer region of SHOX.

Haploinsufficiency of the short stature homeobox-containing (SHOX) gene leads to a phenotypic spectrum ranging from Leri-Weill dyschondrosteosis (LWD) to SHOX-deficient short stature. SHOX nullizygosity leads to Langer mesomelic dysplasia. Pathogenic variants can include whole or partial gene deletions or duplications, point mutations within the coding sequence, and deletions of upstream and downstream regulatory elements. Here we report two families: a non-consanguineous family with a deletion downstream of SHOX, in which the homozygous proband presented with isolated Madelung deformity, without LWD or short stature, as well as a 9-year-old girl with Madelung deformities, mesomelia, a dominant family history of Madelung deformity and a heterozygous deletion of the CNE9 region in the 3' downstream region of SHOX. These case reports provide additional information on the effects of 3' downstream deletions of SHOX, by demonstrating the limited phenotype associated with the recurrent 47.5 kb deletion in a homozygous state and the CNE9 deletion in a heterozygous state.

Identification of a novel mutation of the SHOX gene in a patient with Leri-Weill dyschondrosteosis accompanied by growth hormone deficiency.

Identification of a novel mutation of the SHOX gene in a patient with Leri-Weill dyschondrosteosis accompanied by growth hormone deficiency.

Effect of clinical whole exome sequencing in aetiological investigation and reproductive risk prediction for a couple with monogenic inherited diseases.

To determine the genetic causes of monogenic inherited diseases in a couple using clinical whole exome sequencing (WES) and advise on their reproductive choices. WES was applied to a couple seeking reproductive advice, the female with short stature and the male with congenital cataracts. (1) The woman exhibited a 13.8Kb heterozygous deletion at chrX: 591590-605428 (hg19). This region corresponds to exons 2-6 of the short-stature homeobox-containing (SHOX) gene (NM000451). Associated diseases involving the SHOX gene range from severe Leri-Weill dyschondrosteosis to mild nonspecific short stature. Meanwhile, further validation using a quantitative reverse transcription polymerase chain reaction assay confirmed the heterozygous deletion of the SHOX gene in the proband, as well as other family members with similar clinical characteristics (the proband's mother, aunt, and cousin). Multiple pathogenic reports of this variant have been included in the HGMD database. Per the American College of Medical Genetics and Genomics (ACMG) classification criteria, this deletion is classified as pathogenic. (2) For the male patient, a heterozygous variant was detected in the CRYBB3 gene: NM004076: c.226G>A (p.Gly76R). Variants in the CRYBB3 gene can cause Cataract 22 (OMIM: 609741). At present, this variant locus is not included in databases such as the gnomAD, while both SIFT and PolyPhen2 deem this locus 'damaging'. Moreover, further validation by Sanger sequencing confirmed that the variant was inherited from the male patient's mother, who also had cataracts. According to ACMG standards and guidelines, the c.226G>A (p.Gly76Arg) variant in the CRYBB3 gene is classified as having 'uncertain significance'. WES identified pathogenic variants in both individuals, suggesting a 25% chance of a healthy child naturally. Third-generation assisted reproductive techniques are recommended to minimize the risk of affected offspring.

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

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

Leri-Weill dyschondrosteosis; a rare type of mesomelic short stature in a Sri Lankan family

No abstract available

SHOX Variations in Idiopathic Short Stature in North India and a Review of Cases from Asian Countries

Short stature homeobox (SHOX) haploinsufficiency underlies idiopathic short stature (ISS) and Leri-Weill dyschondrosteosis. The worldwide prevalence of SHOX variations in ISS varies from 2.5% to 15.0%. The aim of this study was to assess the implication of SHOX variation in ISS in North Indians and compare this with other cases of SHOX variations from Asian population. SHOX gene analysis was carried out by multiplex ligation-dependent probe amplification followed by Sanger sequencing in 54 patients with variable phenotypes. Comparison with other reports in a meta-analysis comprising the current study and 11 previous studies (n=979) was performed. SHOX analysis resulted in 12.9% positivity (7.4% deletions and 5.5% duplications). SHOX association was seen significantly related to gender, with predominance in females (p=0.047). Short arms and forearms were the only significantly associated trait seen in 51.9% of children. The overall prevalence of SHOX variation was 15.2% in Asians with ISS. No significant difference was found in geographical region-specific analysis. This study summarises findings from the last decade and provides an updated picture of the prevalence of SHOX variations in Asians, emphasizing their potential as therapeutic targets in ISS patients. Further high quality, large investigations including functional validation is warranted to validate this association.

C16 NONCOMPACTION OF VENTRICULAR MYOCARDIUM AND X–LINKED RECESSIVE ICHTYOSIS

Abstract Noncompact left ventricle is a rare congenital cardiomyopathy characterized by numerous ventricular trabeculae separated by deep intertrabecular recesses. It can occur in isolation or in association with neuromuscular disorders and congenital heart defects. The cause is not known but it is thought to be due to the arrest of the normal maturation process of the myocardium. Among the responsible mutations are taffazzine, ZASP and distrobrevin. It can manifest as left ventricular dilatation and dysfunction, arrhythmias, thromboembolic events, and sepsis. The echocardiogram is the investigation of first choice. Magnetic resonance allows you to more precisely distinguish compact and non–compact layers, thrombi and myocardial fibrosis. Clinical case A 19–year–old patient came for syncope. She presented with midfacial hypoplasia, cupped ears, synophrium, high palate, ichthyosis, small hands, and scarring from Achilles tendon lengthening. She denied a family history of cardiovascular disease and sudden cardiac death. Karyotype analysis showed karyotype 46Y, –X, + der t (X; Y) (p22.2; q11.1), with a chromosome derived from the X;Y translocation (a feature already known in the mother and in several maternal relatives ). Coronary angiography, electroencephalogram and brain MRI were within limits. Echocardiogram and MRI showed non–compact myocardium at the left ventricular apex and mild ventricular dysfunction with areas of anterior and posterior dyssynergia (Fig. 1). The ECG showed high QRS voltages. The Holter ECG showed numerous supraventricular extrasystoles even in pairs and runs, rare PVCs, and nocturnal pauses of up to 3 seconds. The patient underwent genetic screening by NGS for sarcomeric mutations which resulted negative. Subsequent genetic analysis showed deletion in two chromosomal regions that could be interpreted as pathogenic (chromosomal region Xp22.33 containing the SHOX gene and involving the deleted locus in Leri–Weill dyschondrosteosis and in the Xp22.33p22.31 region containing the STS gene involving the locus deleted in X–linked recessive ichthyosis) and a duplication in the chromosomal region Yq11.221q11.23 of uncertain significance. Conclusions After review of the scientific literature, the association of the illustrated complex deletion and translocation with non–compact myocardium represents a new finding, worthy of being explored in genetically affected patients.

Leri–Weill Dyschondrosteosis Caused by a Leaky Homozygous SHOX Splice-Site Variant

SHOX deficiency is a common genetic cause of short stature of variable degree. SHOX haploinsufficiency causes Leri-Weill dyschondrosteosis (LWD) as well as nonspecific short stature. SHOX haploinsufficiency is known to result from heterozygous loss-of-function variants with pseudo-autosomal dominant inheritance, while biallelic SHOX loss-of-function variants cause the more severe skeletal dysplasia, Langer mesomelic dyschondrosteosis (LMD). Here we report for the first time the pseudo-autosomal recessive inheritance of LWD in two siblings caused by a novel homozygous non-canonical, leaky splice-site variant in intron 3 of SHOX: c.544+5G>C. Transcript analyses in patient-derived fibroblasts showed homozygous patients to produce approximately equal amounts of normally spliced mRNA and mRNA with the abnormal retention of intron 3 and containing a premature stop codon (p.Val183Glyfs*31). The aberrant transcript was shown to undergo nonsense-mediated mRNA decay, and thus resulting in SHOX haploinsufficiency in the homozygous patient. Six healthy relatives who are of normal height are heterozygous for this variant and fibroblasts from a heterozygote for the c.544+5G>C variant produced wild-type transcript amounts comparable to healthy control. The unique situation reported here highlights the fact that the dosage of SHOX determines the clinical phenotype rather than the Mendelian inheritance pattern of SHOX variants. This study extends the molecular and inheritance spectrum of SHOX deficiency disorder and highlights the importance of functional testing of SHOX variants of unknown significance in order to allow appropriate counseling and precision medicine for each family individual.

Genetic Analysis and Sonography Characteristics in Fetus with SHOX Haploinsufficiency.

SHOX haploinsufficiency have been commonly found in isolated short stature (ISS) and Léri-Weill dyschondrosteosis (LWD) patients. However, few publications have described the genetic analysis and clinical characteristics of fetuses with SHOX haploinsufficiency. Chromosomal microarray (CMA) were applied in 14,051 fetuses and sequentially whole exome sequence (WES) in 1340 fetuses who underwent prenatal diagnosis during 2016-2021. The analysis and summary of molecular genetics, sonographic characteristics, and follow-up results were performed in fetuses with SHOX haploinsufficiency without other genetic etiologies. A comparison was made between three groups according to prenatal diagnostic indications. 8 (0.06%) fetuses of SHOX haploinsufficiency were all detected by CMA, of which 5 (62.5%) were detected with short long bones by ultrasound scan, and 4 were inherited from their previously undiagnosed parents. No pathogenic SHOX variants were found by WES. The detection rate of SHOX haploinsufficiency was obviously higher in the short long bone group (2.6%, 5/191) than the other abnormality group (0.03%, 1/3919) or no ultrasound abnormality group (0.02%, 2/9941). Three of the fetuses were liveborn with normal growth up to the age of four and four were terminated. The phenotype of fetuses with SHOX haploinsufficiency is highly varied. Over 1/3 of the cases exhibited no phenotype and nearly 2/3 with short long bones, in the absence of Madelung deformity during fetal development. SHOX haploinsufficiency should be considered in all antenatal presentations, especially in the case of isolated short long bones. CMA can provide effective detection.

Clinical impact of variants in non-coding regions of SHOX - Current knowledge.

The short stature homeobox-containing (SHOX) is the most frequently analysed gene in patients classified as short stature patients (ISS) or diagnosed with Leri-Weill dyschondrosteosis (LWD), Langer mesomelic dysplasia (LMD), or Madelung deformity (MD). However, clinical testing of this gene focuses primarily on single nucleotide variants (SNV) in its coding sequences and copy number variants (CNV) overlapping SHOX gene. This review summarizes the clinical impact of variants in noncoding regions of SHOX. RECENT FINDINGS: CNV extending exclusively into the regulatory elements (i.e., not interrupting the coding sequence) are found more frequently in downstream regulatory elements of SHOX. Further, duplications are more frequent than deletions. Interestingly, downstream duplications are more common than deletions in patients with ISS or LWD but no such differences exist for upstream CNV. Moreover, the presence of specific CNVs in the patient population suggests the involvement of additional unknown factors. Some of its intronic variants, notably NM_000451.3(SHOX):c.-9delG and c.-65C>A in the 5'UTR, have unclear clinical roles. However, these intronic SNV may increase the probability that other CNV will arise de novo in the SHOX gene based on homologous recombination or incorrect splicing of mRNA. SUMMARY: This review highlights the clinical impact of noncoding changes in the SHOX gene and the need to apply new technologies and genotype-phenotype correlation in their analysis.

EP342: Clinical testing of SHOX gene for SHOX deficiency disorders

Haploinsufficiency of the short stature homeobox-containing (SHOX) gene causes a range of disorders from the milder phenotype of isolated short stature to the more severe Leri-Weill dyschondrosteosis (LWD). The SHOX gene maps to the pseudoautosomal region of the sex chromosomes, allowing for pseudoautosomal inheritance. Pathogenic SHOX variants on one allele cause LWD and familial short stature, while pathogenic variants on both alleles cause Langer mesomelic dysplasia (LMD). Deletions and duplications of the SHOX coding region, or the enhancer element(s) upstream or downstream of SHOX gene are representative of 80-90% of SHOX disorders, while the rest of the patients were identified to have pathogenic sequence variants.

SHOX whole gene duplications are over-represented in SHOX haploinsufficiency phenotype cohorts.

Transcription of SHOX is dependent upon the interaction of the gene with a complex array of flanking regulatory elements. Duplications that contain flanking regulatory elements but not the SHOX gene have been reported in individuals with SHOX haploinsufficiency syndromes, suggesting that alterations to the physical organisation or genomic architecture may affect SHOX transcription. Individuals with tall stature and an additional X or Y chromosome have an extra copy of both the SHOX gene and the entire SHOX regulatory region, so all three copies of SHOX can be expressed fully. However, for a duplication of the SHOX gene that does not include all of the flanking regulatory elements, the potential effect on SHOX expression is difficult to predict. We present nine unpublished individuals with a SHOX whole gene duplication in whom the duplication contains variable amounts of the SHOX regulatory region, and we review 29 similar cases from the literature where phenotypic data were clearly stated. While tall stature was present in a proportion of these cases, we present evidence that SHOX whole gene duplications can also result in a phenotype more typically associated with SHOX haploinsufficiency and are significantly over-represented in Leri-Weill Dyschondrosteosis and idiopathic short stature probands compared to population controls. Although similar-looking duplications do not always produce a consistent phenotype, there may be potential genotype-phenotype correlations regarding the duplication size, regulatory element content and the breakpoint proximity to the SHOX gene. Although ClinGen (clinicalgenome.org) do not currently consider SHOX whole gene duplications to be clinically significant, the ClinGen triplosensitivity score does not take into account the context of the duplication, and more is now known about SHOX duplications and the role of flanking elements in SHOX regulation. The evidence presented here suggest that these duplications should not be discounted without considering the extent of the duplication and the patient phenotype, and should be included on diagnostic laboratory reports as variants of uncertain significance. Given the uncertain pathogenicity of these duplications, any reports should encourage the exclusion of all other causes of short stature where possible.

Disentangling Turner syndrome and Leri-Weill Dyschondrosteosis; the importance of genetic assessment in the management of Turner Syndrome

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

NPR2 gene variants in familial short stature: a single-center study.

NPR2 variants are associated with various short stature and bone dysplasia, such as acromesomelic dysplasia Maroteaux tyoe, individuals with a phenotype similar to Léri-Weill syndrome (LWD), and idiopathic short stature (ISS). However, few studies have reported on the relationship between familial short stature (FSS) and NPR2 variants. This study aimed to explore the relationship between FSS and NPR2 variants through the detection and identification of NPR2 variants in children with FSS, phenotypic description, clear treatment plan, and follow-up of treatment effect. Children who met the FSS diagnostic criteria and had informed consent were included in the study. The trio whole-exome sequencing method (trio-WES) was used to detect and evaluate the NPR2 variants. A total of 16 children with short stature were included in this study (pretreatment height≤-2 standard deviation (SD) in both the patient and the shorter parent, unknown genetic etiology). NPR2 variants were identified in 12.5%(2/16) of the participants. Patient A was a 6-year-old male and 103.7cm tall (-3.11SD), while Patient B was a 9-year-old female and 123.2cm tall (-1.88SD). However, their heights increased after recombinant human growth hormone (rhGH) treatment. The height of patient A increased by 0.36SD six months after treatment while that of patient B increased by 1.22SD after one and a half years of treatment. NPR2 variant causes FSS. The growth rate of children significantly improved after rhGH treatment. However, further follow-up study is needed to determine the final height after long-term treatment.

Leri-Weill dyschondrosteosis in a newborn presenting with respiratory failure due to severe micrognathia

Leri-Weill dyschondrosteosis in a newborn presenting with respiratory failure due to severe micrognathia

Coexistence of dyschondrosteosis associated to SHOX deficiency, pseudohypoparathyroidism 1B, and chronic autoimmune thyroiditis: a case report

Abstract We present an unusual case of SHOX deficiency associated with Léri-Weill dyschondrosteosis (LWD), Hashimoto’s thyroiditis and pseudohypoparathyroidism 1B in a young woman. To our knowledge, this is the first ever report of these disorders coexisting. At the age of nine years, the proband was diagnosed of hypothyroidism due to Hashimoto’s thyroiditis, and developed biochemical abnormalities consistent with hyperphosphatemia, mild hypocalcemia and elevated parathyroid hormone without any clinical symptoms except short stature. Replacement therapy with levothyroxine, calcium and alphacalcidol was initiated. The diagnosis of pseudohypoparathyroidism 1B was confirmed at the age of 17.5 years with the demonstration of methylation alteration at the GNAS locus. At the age of 16 years, 3.5 years after her menarche, she presented clear features of LWD. A large deletion of the SHOX gene was confirmed. Family genetic tests were not doable since she was adopted. We discuss the diagnostic challenges of these coexisting rare endocrinopathies.

Detection of <i>SHOX</i> 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.

Short stature and SHOX (Short stature homeobox) variants-efficacy of screening using various strategies.

BackgroundSHOX mutations have previously been described as causes of Léri-Weill dyschondrosteosis (LWD), Langer mesomelic dysplasia (LMD), and idiopathic short stature. The loss of X chromosome—Turner syndrome or mosaic 45,X/46,XX or 46,XY—also leads to the heterozygous loss of SHOX in patients with short stature only or with features similar to LWD. The aim of this study was to assess the efficacy of the targeted screening for SHOX variants, which involved different methods in the laboratory analysis of short stature. We determined the significance and positive predictive value of short stature for the detection of SHOX variants.MethodsTargeted screening for variants in SHOX involving MLPA, sequencing, karyotyping and FISH was performed in the short stature cohort (N = 174) and control cohort (N = 91). The significance of short stature and particular characteristics for the detection of SHOX variants was determined by Fisher’s exact test, and the probability of SHOX mutation occurrence was calculated using a forward/stepwise logistic regression model.ResultsIn total, 27 and 15 variants influencing SHOX were detected in the short stature and control cohorts, respectively (p > 0.01). Sex chromosome aberrations and pathogenic CNV resulting in diagnosis were detected in eight (4.6%) and five (2.9%) patients of the short stature group and three (3.3%) and one (1.1%) individuals of the control group. VUS variants were discovered in 14 (8.0%) and 11 (12.1%) individuals of the short stature and control groups, respectively. MLPA demonstrated the detection rate of 13.22%, and it can be used as a frontline method for detection of aberrations involving SHOX. However, only mosaicism of monosomy X with a higher frequency of monosomic cells could be reliably discovered by this method. Karyotyping and FISH can compensate for this limitation; their detection rates in short stature group were 3.55% and 13.46% (N = 52), respectively. FISH proved to be more effective than karyotyping in the study as it could reveal cryptic mosaics in some cases where karyotyping initially failed to detect such a clone. We suggest adding FISH on different tissue than peripheral blood to verify sex-chromosome constitution, especially in cases with karyotypes: 45,X; mosaic 45,X/46,XX or 46,XY; 46,Xidic(Y) detected from blood; in children, where mosaic 45,X was detected prenatally but was not confirmed from peripheral blood. The correlation of short stature with the occurrence of SHOX mutations was insignificant and short stature demonstrates a low positive predictive value-15.5% as unique indicator for SHOX mutations. The typical skeletal signs of LWD, including Madelung deformity and disproportionate growth, positively correlate with the findings of pathogenic SHOX variants (p < 0.01) by Fisher’s exact test but not with the findings of VUS variants in SHOX which are more prevalent in the individuals with idiopathic short stature or in the individuals with normal height.

Variants in the 5\u2032UTR reduce SHOX expression and contribute to SHOX haploinsufficiency

SHOX haploinsufficiency causes 70–90% of Léri-Weill dyschondrosteosis (LWD) and 2–10% of idiopathic short stature (ISS). Deletions removing the entire gene or enhancers and point mutations in the coding region represent a well-established cause of haploinsufficiency. During diagnostic genetic testing on ISS/LWD patients, in addition to classic SHOX defects, five 5′UTR variants (c.-58G > T, c.-55C > T, c.-51G > A, c.-19G > A, and c.-9del), were detected whose pathogenetic role was unclear and were thus classified as VUS (Variants of Uncertain Significance). The purpose of the present study was to investigate the role of these noncoding variations in SHOX haploinsufficiency. The variants were tested for their ability to interfere with correct gene expression of a regulated reporter gene (luciferase assay). The negative effect on the mRNA splicing predicted in silico for c.-19G > A was assayed in vitro through a minigene splicing assay. The luciferase assay showed that c.-51G > A, c.-19G > A, and c.-9del significantly reduce luciferase activity by 60, 35, and 40% at the homozygous state. Quantification of the luciferase mRNA showed that c.-51G > A and c.-9del might interfere with the correct SHOX expression mainly at the post-transcriptional level. The exon trapping assay demonstrated that c.-19G > A determines the creation of a new branch site causing an aberrant mRNA splicing. In conclusion, this study allowed us to reclassify two of the 5′UTR variants identified during SHOX diagnostic screening as likely pathogenic, one remains as a VUS, and two as likely benign variants. This analysis for the first time expands the spectrum of the genetic causes of SHOX haploinsufficiency to noncoding variations in the 5′UTR.

SAT-LB17 Triplication of SHOX Downstream Region in Mild Short Stature

Deletions of the downstream flanking regions of the SHOX gene that contain conserved non-coding cis-regulatory DNA elements are a known cause of Leri-Weill dyschondrosteosis or idiopathic short stature (ISS). Functional and comparative genomic studies have demonstrated the existence of four CNE enhancers downstream of SHOX which have transcriptional activity, and a fifth has recently been suggested at approximately X:970,000. Duplications of these downstream regions have also been described in patients with ISS, although with a variable phenotype. We present a family with ISS and the first ever reported SHOX downstream triplication. The index case was a 12-year-old Caucasian female of unrelated parents, born with normal weight and length, and normal hearing/vision and development. At the age of 12, her height was -1.87 SD (-1.35 SD adjusted for parental height). Her growth chart showed a height on the 90th centile at birth, slowly crossing centiles for the first 5 years to the 2nd centile, which she then followed. She had normal proportions and head circumference, and no dysmorphic features apart from inverted nipples. Baseline investigations for short stature were normal, including IGF1, karyotype and celiac screen. Bone age was 1.5 year delayed. Family history: arthritis in the father, early menopause in the mother. Analysis of SHOX and its flanking regions was carried out using Multiplex Ligation-dependent Probe Amplification (MLPA) and direct sequencing of all coding exons. MLPA analysis showed a SHOX downstream triplication with a minimum size of 66kb (X:963670-1029779) and a maximum size of 428kb (X:899389-1327688). The size of the duplication was further defined using array comparative genome hybridization (ACGH) analysis which showed the minimum size to be ~325kb (X:907457-1232802). This triplication includes the proposed regulatory element at ~ X:970,000. The triplication was subsequently shown to be present in the proband’s mother and brother who also have mild ISS. Further analysis of these and other family members is ongoing. The triplication is of a single-sized fragment, and the fragment size is identical to one that has been seen in duplicated form in several other patients, increasing the likelihood that the triplicated fragments are in tandem. The precise mechanism of the pathogenic effect of the triplication is unknown, but it likely exerts a negative effect on SHOXtranscription, reducing its expression and ultimately resulting in SHOX haploinsufficiency. In conclusion, we describe a family with mild ISS and a downstream triplication of the proposed X:970,000 SHOX downstream regulatory element. This provides further evidence for this previously proposed regulatory element downstream of SHOX and adds additional proof that increased dosage of this regulatory element region is a cause of short stature.