Skeletal Deformity Associated with SHOX Deficiency

Presence of anomalous flexor carpi radialis brevis (FCRB) in Madelung's deformity

An anomalous flexor carpi radialis brevis (FCRB) muscle was present in four of nine patients undergoing surgery for Madelung's deformity. This disproportionately frequent finding suggests an embryologic dysgenesis of forearm formation rather than a developmental tethering of Vicker's ligament.Level of evidence: IV (case series).

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.

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.

State of the art review: The pathogenesis and management of Madelung deformity

Madelung deformity remains a fascinating yet unresolved challenge. There is an increasing awareness for early diagnosis by healthcare providers with improvement in diagnostic modalities, however, the exact mechanisms for the development of the deformity have still to be clarified. While some corrective procedures have been described to effectively address an established deformity, the existing literature lacks clear and evidence-based treatment guidelines on how to proceed in daily practice. This review article aims to summarize the current best evidence on this topic, including particular areas of controversy and areas with need for future research.

SHOX far-downstream deletion in a patient with nonsyndromic short stature

Haploinsufficiency of SHOX represents one of the major genetic causes of nonsyndromic short stature. To date, eight DNA elements around SHOX exons have been proposed as putative enhancer regions. Although six copy-number variations (CNVs) downstream to the known enhancer regions have recently been identified in patients with short stature, the pathogenicity of these CNVs remains uncertain. Here, we identified a paternally derived SHOX far-downstream deletion in a boy. The deletion involved a ~100 kb genomic interval at a position >60 kb away from the known enhancer regions. The boy exhibited moderate short stature with nonspecific skeletal changes. The height of the father was within the normal range but lower than the mid-parental height. The deletion of the boy and the six previously reported CNVs mostly overlapped; however, all CNVs had unique breakpoints. The deletion of our case encompassed a ~30 kb genomic interval that has previously been associated with a 4C-seq peak, as well as several SHOX-regulatory SNPs/indels. These results indicate that the SHOX far-downstream region contains a novel cis-acting enhancer, whose deletion leads to nonsyndromic short stature of various degree. In addition, our data highlight genomic instability of SHOX-flanking regions that underlies diverse nonrecurrent CNVs.

Factors affecting prepubertal and pubertal bone age progression

Bone age (BA) is a clinical marker of bone maturation which indicates the developmental stage of endochondral ossification at the epiphysis and the growth plate. Hormones that promote the endochondral ossification process include growth hormone, insulin-like growth factor-1, thyroid hormone, estrogens, and androgens. In particular, estrogens are essential for growth plate fusion and closure in both sexes. Bone maturation in female children is more advanced than in male children of all ages. The promotion of bone maturation seen in females before the onset of puberty is thought to be an effect of estrogen because estrogen levels are higher in females than in males before puberty. Sex hormones are essential for bone maturation during puberty. Since females have their pubertal onset about two years earlier than males, bone maturation in females is more advanced than in males during puberty. In the present study, we aimed to review the factors affecting prepubertal and pubertal BA progression, BA progression in children with hypogonadism, and bone maturation and deformities in children with Turner syndrome.

Retrospective study of radial dome osteotomy with volar plate fixation versus K-wires in Madelung's deformity: long-term follow-up

PURPOSE

The emerging role of the locking plate improved the technique also in corrective osteotomies in Madelung's deformity, but there is a lack of analyses between the fixation techniques, as well as little information in functional outcomes and long-term follow-up. The current study compared the outcomes, pitfalls, and advantages of volar plate and screws fixation versus K-wires fixation in a long-term follow-up.

METHODS

Twenty-eight children presenting the "distal radius" variant of Madelung's deformity underwent Vickers ligament release and distal radial dome osteotomy between 2009 and 2015. Twenty-three children (20 females and 3 males, mean age 15 years and 7 months at surgery and 24 years and 8 moths at follow-up), with 26 operatively treated wrists, were available for follow-up. A retrospective two-cohort study, evaluating clinically and radiologically results, has been conducted with a mean eight years and seven months follow-up.

RESULTS

Bone union and pain relief were obtained in all cases, as well as improvements in wrist motion and radiographic indices. A statistically significant correlation was identified between the volar plate fixation and an improved lunate subsidence on X-ray, and a trend towards an improved DASH score in the cohort with plate and screws, as well as significant improvement in wrist extension and supination always in the plate fixation cohort.

CONCLUSIONS

The long-term follow-up enabled the patients to report on more definitive outcomes in terms of functional and cosmetic improvements. Volar plate fixation is an effective technique allowing for simple post-operative management and earlier rehabilitation program with improved clinical and radiographic outcomes.

Reverse wedge osteotomy for Madelung's deformity in a high school student: A case report

Madelung deformity is a congenital disorder with the malformation of anterior ulnar bowing of radius and a dorsally protruding ulnar head caused by premature growth disturbance at the medial volar aspect of the distal radius. This report describes a bilateral idiopathic Madelung deformity in a 17-year-old woman treated successfully using reverse wedge osteotomy of the distal radius in a symptomatic left wrist. Reverse wedge osteotomy can orient the radial joint surface while correcting the whole radius length by reversely putting the wedge bone removed from the distal metaphysis of radius, the base of which is cut from the surplus of the radial and dorsal cortical bone in the hypotrophic portion. We corrected the palmar subluxation of the carpus, restored her good function, and relieved her wrist pain.

Modified dome osteotomy and anterior locking plate fixation for distal radius variant of Madelung deformity: a retrospective study

PURPOSE

Dome osteotomy of the distal radius with Vickers ligament release is an established method of treatment for Madelung deformity. Many different surgical procedures have been proposed in literature but techniques, patient inclusion and efficacy evaluations are heterogeneous.

MATERIALS AND METHODS

A retrospective review of children affected by 'distal radius' Madelung deformity and treated with a standardized surgical procedure (modified reverse dome osteotomy of the distal radius and volar fixation with a small locking plate) between 2010 and 2018 at a single center was performed. The technique used in this study, reversing the shape of the classical dome osteotomy, allowed for an improved three-planar correction of the distal radial epiphysis and volar plate fixation allowed for an increased stability and reduced soft tissue morbidity. A structured follow-up including a prompt post-operative rehabilitation program (without wrist immobilization) was established. Pain relief, functional outcome and cosmetic appearance were assessed with a structured clinical assessment, DASH Score and radiographic assessment, accordingly.

RESULTS

A total of 15 wrists in 13 children (12 females, mean age of 15.6 years, range 11-19) were included. The mean follow-up time was 3.8 years. Bone union and pain relief were obtained in all cases. Improvement in the range of motion was detected in extension, supination and flexion of the wrist. Radial inclination was increased by 15.3° and lunate subsidence by 4.1 mm.

CONCLUSIONS

The use of volar fixation with a small locking plate and immediate post-operative rehabilitation for reverse dome osteotomy of the distal radius in pediatric patients affected by 'distal radius' Madelung's deformity is stable and effective.

Radiotriquetral Ligament in Madelung's Deformity Associated with Leri-Weill's Dyschondrosteosis

Madelung's deformity (MD) is frequently associated with Leri-Weill's dyschondrosteosis (LWD) even if the primary isolated form (PI-MD) is much more common.

Recent studies pointed out how two abnormal ligaments, the Vickers ligament (VL) and the radiotriquetral ligament (RTL), are defining traits of MD. To date, in PI-MD, both VL and RTL have been reported. In MD associated with LWD (LWD-MD), the VL is also present, but the RTL has never been reported.

We herein report the first case of MD associated with a genetically confirmed LDW with an RTL, detected on MRI.

This report describes the MRI imaging features of MD-LWD, which have not been adequately characterized in previous literature.

Heterozygous Deletion of the SHOX Gene Enhancer in two Females With Clinical Heterogeneity Associating With Skewed XCI and Escaping XCI

Skewed X-chromosome inactivation (XCI) plays an important role in the phenotypic heterogeneity of X-linked disorders. However, the role of skewed XCI in XCI-escaping gene SHOX regulation is unclear. Here, we focused on a heterozygous deletion of SHOX gene enhancer with clinical heterogeneity. Using SNP array, we detected that the female proband with Leri-Weill dyschondrosteosis (LWD) carried an 857 kb deletion on Xp22.3 (encompassing SHOX enhancer) and a 5,707 kb large-fragment deletion on Xq25q26. XCI analysis revealed that the X-chromosome with the Xq25q26 large-fragment deletion was completely inactivated, which forced the complete activation of the other X-chromosome carrying SHOX enhancer deletion. While the Xp22.3 deletion locates on the escaping XCI region, under the combined action of skewed XCI and escaping XCI, transcription of SHOX gene was mainly from the activated X-chromosome with SHOX enhancer defect, involving in the formation of LWD phenotype. Interestingly, this SHOX enhancer deletion was inherited from her healthy mother, who also demonstrated completely skewed XCI. However, the X-chromosome with SHOX enhancer deletion was inactivated, and the normal X-chromosome was activated. Combing with escaping XCI, her phenotype was almost normal. In summary, this study was a rare report of SHOX gene enhancer deletion in a family with clinical heterogeneity due to skewed inactivation of different X-chromosomes, which can help in the genetic counseling and prenatal diagnosis of disorders in females with SHOX defect.

Sonographic Findings in Adult Congenital Madelung Deformity: A Case Study

This case study describes six sonographic findings, with correlative imaging, in an adult patient with congenital Madelung deformity. Two are typical of congenital Madelung deformity: a thick volar hyperechoic band extending from the ulnar side of the distal radius toward the lunate-triquetrum area, the so-called Vickers ligament, adjacent to the radiotriquetral ligament, and a cortical defect on the ulnar and volar side of the distal radius. Other findings may be also observed, such as a narrowed distance between the Lister tubercle and the distal radioulnar joint, a dorsal subluxation of the ulnar head, an extensor tendons entrapment and pronator quadratus modifications. Although the diagnosis of congenital Madelung deformity is based usually on clinical examination, this rare malformation may remain undiscovered until adulthood. When sonography is used as the first imaging technique, the sonographic findings of congenital Madelung deformity can facilitate diagnosis and the appropriate radiographs.

Leri-Weill Dyschondrosteosis Syndrome: Analysis via 3DCT Scan

Background: Leri-Weill dyschondrosteosis (LWD) is a pseudoautosomal form of skeletal dysplasia, characterized by abnormal craniofacial phenotype, short stature, and mesomelia of the upper and lower limbs. Methods: We describe two female patients with LWD. Their prime clinical complaints were severe bouts of migraine and antalgic gait. Results: Interestingly, via a 3D reconstruction CT scan we encountered several major anomalies. Notable features of craniosynostosis through premature fusion of the squamosal sutures and partial closure of the coronal sutures were the reason behind the development of abnormal craniofacial contour. A 3D reconstruction CT scan showed apparent bulging of the clavarium through the partially synostosed coronal and totally synostosed squamosal sutures. Additional deformities include deficient number of ribs (10 ribs on both sides), defective ossification of the ischium and dysplasia of the iliac-ischial junction, and coxa valga have been noted. Conclusions: The constellation of observed deformities can be considered as a novel features associated with LWD.

Dental and Maxillofacial Signs in Leri-Weill Dyschondrosteosis

One of the most common causes of short stature is a defect of the short stature homeobox-containing (SHOX) gene, which is located in pseudoautosomal region 1 on the distal end of the short arm of chromosomes Xp22.33 and Yp11.32. More than 300 different mutations in the SHOX gene responsible for short stature syndrome have been described. The phenotypic expression of SHOX haploinsufficiency is remarkably varied. The 3 typical clinical presentations, from least to most severe, are idiopathic short stature without skeletal malformations, Leri-Weill dyschondrosteosis (LWD), and Langer mesomelic dysplasia, which is believed to represent the homozygous form of LWD. Despite a higher prevalence in women, suggesting the potentiating action of high estrogen levels on the effects of SHOX deficiency, the syndrome was initially believed to have an autosomal pattern of inheritance. In reality, heterozygous SHOX mutations can be transferred from the Y to the X chromosome and vice versa. This phenomenon is called "the jumping SHOX gene" and corresponds to a pseudoautosomal dominant inheritance. LWD is characterized by mesomelic short stature and Madelung deformity defined by an upward and medial displacement of the radial joint surface, which restricts range of motion. Less specific dysmorphic signs associated with LWD, such as short hands and feet, scoliosis, or muscular hypertrophy, have been described. When reviewing the dental and maxillofacial signs, only limited and summary data (micrognathia and high arched palate) have been published in the literature. This report presents a case of LWD that highlights many other noteworthy dental and maxillofacial signs that are important to clearly identify and appropriately treat.

Identification of a limb enhancer that is removed by pathogenic deletions downstream of the SHOX gene

Haploinsufficiency of the human SHOX gene causes Léri-Weill dyschondrosteosis (LWD), characterized by shortening of the middle segments of the limbs and Madelung deformity of the wrist. As many as 35% of LWD cases are caused by deletions of non-coding sequences downstream of SHOX that presumably remove an enhancer or enhancers necessary for SHOX expression in developing limbs. We searched for these active sequences using a transgenic mouse assay and identified a 563 basepair (bp) enhancer with specific activity in the limb regions where SHOX functions. This enhancer has previously escaped notice because of its poor evolutionary conservation, although it does contain 100 bp that are conserved in non-rodent mammals. A primary cell luciferase assay confirmed the enhancer activity of the conserved core sequence and demonstrated that putative HOX binding sites are required for its activity. This enhancer is removed in most non-coding deletions that cause LWD. However, we did not identify any likely pathogenic variants of the enhancer in a screen of 124 LWD individuals for whom no causative mutation had been found, suggesting that only larger deletions in the region commonly cause LWD. We hypothesize that loss of this enhancer contributes to the pathogenicity of deletions downstream of SHOX.

A rare unbalanced Y:autosome translocation in a Turner syndrome patient

BACKGROUND

Y:autosome translocations are reported to be associated with male infertility and azoospermia. Female cases with Y:autosome translocation are extremely rare.

CASE PRESENTATION

We report a unique case of a rare unbalanced translocation t(Y;13) in a 12-year-old girl with Turner syndrome. Combined cytogenetic testing helped to demonstrate the detail of rare chromosomal structural rearrangement in this patient.

CONCLUSIONS

The presented case showed femaleness phenotype and failure of masculinization with presence of Y chromosome and the SRY gene. She was treated with growth hormone (GH) therapy after confirming the presence of only female internal gonad with laparoscopy.

Acute lymphoblastic leukemia in a child with Leri-Weill syndrome and complete SHOX gene deletion: A Case Report

BACKGROUND

Leri-Weill syndrome (LWS) ranks among conditions with short stature homeobox gene (SHOX) haploinsufficiency. Data on possible association of SHOX aberrations with malignant diseases are scarce.

METHODS AND RESULTS

We report a unique case of an 8-year-old girl who was successfully treated for acute lymphoblastic leukemia (pre-B ALL, intermediate risk) and was subsequently diagnosed with LWS due to characteristic clinical appearance (short disproportionate stature, Madelung deformity of the wrist) and molecular genetic examination (complete deletion of SHOX). An identical SHOX deletion was identified also in the patient's mother. Leukemic cells of the patient were retrospectively examined by array comparative genomic hybridization (aCGH), which revealed five regions of deletions at chromosome X, including the SHOX gene locus.

CONCLUSION

Growth retardation in children with hemato-oncologic malignancies cannot always be attributed to cytotoxic treatment and should be carefully evaluated, especially with regards to growth hormone therapy.

SHOX deficiency in short Taiwanese children: A single-center experience

BACKGROUND

SHOX deficiency is a common cause of idiopathic short stature. The aim of this study was to describe the clinical characteristics and molecular findings of patients with SHOX deficiency in Taiwan.

METHODS

A phenotype scoring system was used to evaluate several anthropometric measures in patients with idiopathic short stature. Twenty-three patients with a phenotype score >7 were enrolled for SHOX gene analysis by MLPA and sequencing. Another patient with a deletion/insertion of the short arm of the X chromosome containing the SHOX gene was enrolled for the assessment.

RESULTS

SHOX deficiency was detected in 26% of short children with a phenotype score >7. The arm-span-to-height ratio was significantly lower in SHOX-D patients than in non-SHOX-D patients. In patients with SHOX deficiency, an arm-span-to-height ratio <96.5% and short forearm were the most common characteristics. Three patients also exhibited typical radiological findings. A molecular analysis of the SHOX gene revealed five patients with intragenic deletions, one with a deletion in the regulatory region, and one with a missense mutation at exon 5.

CONCLUSION

The phenotype scoring system is useful to select children with SHOX deficiency in Taiwan. Family history and radiological image of the radius are also of value for the diagnosis. This study may aid physicians in the early diagnosis of children with SHOX deficiency.

A case of 45,X/47,XXX mosaic Turner syndrome with limb length discrepancy

Patients with Turner syndrome (TS) frequently show short stature and skeletal deformities, such as kyphosis and scoliosis. However, to the best of our knowledge, limb length discrepancy (LLD) has not yet been reported in patients with TS. The case of a 12-yr-old girl with 45,X/47,XXX mosaic TS showing LLD is herein presented. She was on GH therapy for short stature and was noted to have scoliosis in the standing position at a regular examination; however, the scoliosis became less evident in the supine position, which is indicative of LLD. The length of the left leg was 5.0 cm shorter than that of the right leg when measured. She was referred to orthopedics and underwent right distal femoral and right proximal tibial staple epiphysiodesis to shorten the abnormally long limb at 10 yr 6 mo of age. One year after the operation, the LLD decreased from 5.0 to 1.5 cm. During this period, GH was continued. LLD is a rare complication in TS, but when patients with TS show scoliosis in the standing position, re-evaluation for scoliosis in the supine position should be performed and the lengths of both legs should be measured.

Genotype-Phenotype Relationship in Patients and Relatives with SHOX Region Anomalies in the French Population

BACKGROUND

The aim of our study was to describe a large population with anomalies involving the SHOX region, responsible for idiopathic short stature and Léri-Weill dyschondrosteosis (LWD), and to identify a possible genotype/phenotype correlation.

METHODS

We performed a retrospective multicenter study on French subjects with a SHOX region anomaly diagnosed by multiplex ligation-dependent probe amplification or Sanger sequencing. Phenotypes were collected in each of the 7 genetic laboratories practicing this technique for SHOX analysis.

RESULTS

Among 205 index cases and 100 related cases, 91.3% had LWD. For index cases, median age at evaluation was 11.7 (9.0; 15.9) years and mean height standard deviation score was -2.3 ± 1.1. A deletion of either SHOX or PAR1 or both was found in 74% of patients. Duplications and point mutations/indels affected 8 and 18% of the population, respectively. Genotype-phenotype correlation showed that deletions were more frequently associated with Madelung deformity and mesomelic shortening in girls, as well as with presence of radiologic anomalies, than duplications.

CONCLUSIONS

Our results highlight genotype-phenotype relationships in the French population with a SHOX defect and provide new information showing that clinical expression is milder in cases of duplication compared to deletions.

Rare congenital chromosomal aberration dic(X;Y)(p22.33;p11.32) in a patient with primary myelofibrosis

BACKGROUND

Constitutional translocations between sex chromosomes are rather rare in humans with breakpoints at Xp11 and Yq11 as the most frequent. Breakpoints on the short arm of the Y chromosome form one subgroup of t(X;Y), giving rise to a derived chromosome with the centromeres of both the X and Y chromosomes, dic(X;Y). Here, we report a rare congenital chromosomal aberration, 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10], in an adult male.

CASE PRESENTATION

Primary myelofibrosis, a malignant haematological disease, was diagnosed in a 63-year-old man following liver transplantation after hepatocellular carcinoma. By the analysis of the bone marrow sample, the karyotype 46,X,dic(X;Y)(p22.33;p11.32) was detected in all the mitoses analysed and verified with multicolour fluorescence in situ hybridization (mFISH). A cytogenetic examination of stimulated peripheral blood cells revealed the constitutional karyotype 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10]. The cell line 45,X was confirmed with FISH in 35 % of interphase nuclei. The SRY locus was present on the dicentric chromosome. A CGH/SNP array (Illumina) revealed a gain of 153,7 Mbp of the X chromosome and a 803-kbp microdeletion (including the SHOX gene), which were also confirmed with FISH. SHOX encodes a transcriptional factor that regulates the growth of the long bones. The deletion of the SHOX gene together with the Madelung deformity of the forearm and the short stature of the proband led to a diagnosis of Léri-Weill dyschondrosteosis (LWD). The gain of almost the whole X chromosome (153,7 Mbp) was considered a variant of Klinefelter syndrome (KS). The levels of gonadotropins and testosterone were consistent with gonadal dysfunction. A malformation of the right external ear was detected.

CONCLUSIONS

We have reported a structural aberration of the sex chromosomes, dic(X;Y)(p22.33;p11.32). The related genomic imbalance is associated with two known hereditary syndromes, LWD and a KS variant, identified in our proband at an advanced age. Because the breakpoints did not involve cancer genes, we inferred that the two malignancies in the proband were not caused by this abnormality. The possible influence of SHOX haploinsufficiency on the growth regulation of auricular chondrocytes is discussed.

A Track Record on SHOX: From Basic Research to Complex Models and Therapy

SHOX deficiency is the most frequent genetic growth disorder associated with isolated and syndromic forms of short stature. Caused by mutations in the homeobox gene SHOX, its varied clinical manifestations include isolated short stature, Léri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. In addition, SHOX deficiency contributes to the skeletal features in Turner syndrome. Causative SHOX mutations have allowed downstream pathology to be linked to defined molecular lesions. Expression levels of SHOX are tightly regulated, and almost half of the pathogenic mutations have affected enhancers. Clinical severity of SHOX deficiency varies between genders and ranges from normal stature to profound mesomelic skeletal dysplasia. Treatment options for children with SHOX deficiency are available. Two decades of research support the concept of SHOX as a transcription factor that integrates diverse aspects of bone development, growth plate biology, and apoptosis. Due to its absence in mouse, the animal models of choice have become chicken and zebrafish. These models, therefore, together with micromass cultures and primary cell lines, have been used to address SHOX function. Pathway and network analyses have identified interactors, target genes, and regulators. Here, we summarize recent data and give insight into the critical molecular and cellular functions of SHOX in the etiopathogenesis of short stature and limb development.

Systematic molecular analyses of SHOX in Japanese patients with idiopathic short stature and Leri-Weill dyschondrosteosis

The etiology of idiopathic short stature (ISS) and Leri-Weill dyschondrosteosis (LWD) in European patients is known to include SHOX mutations and copy-number variations (CNVs) involving SHOX and/or the highly evolutionarily conserved non-coding DNA elements (CNEs) flanking the gene. However, the frequency and types of SHOX abnormalities in non-European patients and the clinical importance of mutations in the CNEs remains to be clarified. Here, we performed systematic molecular analyses of SHOX for 328 Japanese patients with ISS or LWD. SHOX abnormalities accounted for 3.8% of ISS and 50% of LWD cases. CNVs around SHOX were identified in 16 cases, although the ~47 kb deletion frequently reported in European patients was absent in our cases. Probably damaging mutations and benign/silent substitutions were detected in four cases, respectively. Although CNE-linked substitutions were detected in 15 cases, most of them affected poorly conserved nucleotides and were shared by unaffected individuals. These results suggest that the frequency and mutation spectrum of SHOX abnormalities are comparable between Asian and European patients, with the exception of a European-specific downstream deletion. Furthermore, this study highlights the clinical importance and genetic heterogeneity of the SHOX-flanking CNVs, and indicates a limited clinical significance of point mutations in the CNEs.

SHOX Haploinsufficiency as a Cause of Syndromic and Nonsyndromic Short Stature

SHOX in the short arm pseudoautosomal region (PAR1) of sex chromosomes is one of the major growth genes in humans. SHOX haploinsufficiency results in idiopathic short stature and Léri-Weill dyschondrosteosis and is associated with the short stature of patients with Turner syndrome. The SHOX protein likely controls chondrocyte apoptosis by regulating multiple target genes including BNP,Fgfr3, Agc1, and Ctgf. SHOX haploinsufficiency frequently results from deletions and duplications in PAR1 involving SHOX exons and/or the cis-acting enhancers, while exonic point mutations account for a small percentage of cases. The clinical severity of SHOX haploinsufficiency reflects hormonal conditions rather than mutation types. Growth hormone treatment seems to be beneficial for cases with SHOX haploinsufficiency, although the long-term outcomes of this therapy require confirmation. Future challenges in SHOX research include elucidating its precise function in the developing limbs, identifying additional cis-acting enhancers, and determining optimal therapeutic strategies for patients.

A Leri-Weill dyschondrosteosis patient confirmed by mutation analysis of SHOX gene

Leri-Weill dyschondrosteosis is characterized by SHOX deficiency, Madelung deformity, and mesomelic short stature. In addition, SHOX deficiency is associated with idiopathic short stature, Turner syndrome, and Langer mesomelic dysplasia. We report the first case of a Leri-Weill dyschondrosteosis patient confirmed by SHOX gene mutation analysis in Korea. The patient, who was a 7-year-old female, showed short stature. Her height and weight were 108.9 cm (<3rd percentile) and 19.7 kg (5th-10th percentile), respectively. Her arm span, height of trunk, leg length, and sitting length were 100.5 cm, 58 cm, 50.9 cm, and 62.5 cm, respectively. Her body proportion was 1.13:1. Extremities to trunk ratio was 2.61. Her hand radiograph showed Madelung deformity. And the growth hormone stimulation test showed a normal response. Furthermore, because of Madelung deformity with idiopathic short stature, she was suspected of SHOX deficiency. We performed SHOX gene mutation analysis and found a c.491G>A (p.W164X) mutation of the SHOX gene. Accordingly, this patient was diagnosed with Leri-Weill dyschondrosteosis. Recently, many mutations have been reported in the SHOX gene. However, to date, mutation analysis of the SHOX gene for Leri-Weill dyschondrosteosis has not been reported in Korea as yet. We report the first case of a Leri-Weill dyschondrosteosis patient confirmed by mutation analysis of the SHOX gene.