Baixa estatura por haploinsuficiência do gene SHOX: do diagnóstico ao tratamento

Karyotype Abnormalities in the X Chromosome Predict Response to the Growth Hormone Therapy in Turner Syndrome

Short stature is characteristic for Turner syndrome (TS) patients, and particular karyotype abnormalities of the X chromosome may be associated with different responsiveness to recombinant human GH (rhGH) therapy. The aim of the study was to analyze the effect of different types of TS karyotype abnormalities on the response to rhGH therapy. A total of 57 prepubertal patients with TS treated with rhGH with a 3 year follow-up were enrolled in the study and categorized according to their karyotype as X monosomy (n = 35), isochromosome (n = 11), marker chromosome (n = 5), or X-mosaicism (n = 6). Height and height velocity (HV) were evaluated annually. In the first year, all groups responded well to the therapy. In the second year, HV deteriorated significantly in X-monosomy and isochromosome in comparison to the remaining two groups (p = 0.0007). After 3 years of therapy, all patients improved the score in comparison to their target height, but better outcomes were achieved in patients with marker chromosome and X-mosaicism (p = 0.0072). X-monosomy or isochromosome determined a poorer response during the second and third year of rhGH therapy. The results of the study indicate that the effects of rhGH therapy in patients with TS may depend on the type of TS karyotype causing the syndrome.

A case of premature ovarian failure in a 33-year-old woman

Objective. To assess aetiology of a POF in a 33-year-old woman and, if possible, plan a cure. Design. Case report. Setting. medical genetics diagnostic unit in a university hospital. Patient. A 33-year-old woman with premature ovarian failure (POF). Intervention(s). Genetic counseling, karyotyping, FISH study. Result(s). Turner-like diagnosis. Conclusion(s). Most cases of POF remain idiopathic. Turner syndrome can occur in very different phenotypes; cytogenetic and molecular profiling can provide a definitive diagnosis in cases with nonclassical phenotype.

Clinical and molecular characterization of Chilean patients with Léri-Weill dyschondrosteosis

AIM

Léri-Weill dyschondrosteosis (LWD) is a mesomelic dysplasia with disproportionate short stature associated with short stature homeobox-containing gene (SHOX) haploinsufficiency. The objective of this study was to improve the diagnosis of patients with suspected LWD through molecular analysis.

METHODS

Twelve patients from 11 families with a clinical diagnosis of LWD were analyzed with multiplex ligation-dependent probe amplification to detect deletions and duplications of SHOX and its enhancer regions. High resolution melting and sequencing was employed to screen for mutations in SHOX coding exons.

RESULTS

The molecular-based screening strategy applied in these patients allowed detection of five SHOX deletions and two previously unreported SHOX missense mutations.

CONCLUSION

Molecular studies confirmed the clinical diagnosis of LWD in seven out of 12 patients, which provided support for therapeutic decisions and improved genetic counseling in their families.

The role of the SHOX gene in the pathophysiology of Turner syndrome

Turner syndrome (TS) affects 1:2500 live females. It is caused by partial or complete absence of a sex chromosome. Patients with deletions of the distal segment of the short arm of X chromosome (Xp-) including haploinsufficiency of the SHOX (short stature homeobox) have, more often, short stature, skeletal abnormalities and hearing impairments. This article evaluates the current knowledge of the SHOX gene role in TS pathophysiology. Articles were searched from MEDLINE and LILACS databases, in the past 10 years, using the following keywords: Turner syndrome, SHOX gene, haploinsufficiency, short stature and hearing loss. As the inheritance of only one copy of the SHOX gene does not explain most of TS anomalies, more studies are needed to explain them. These studies will also improve understanding how SHOX participates in cartilage and bone growth and will help develop novel therapeutic strategies focused on SHOX-related disorders.

Improved molecular diagnostics of idiopathic short stature and allied disorders: quantitative polymerase chain reaction-based copy number profiling of SHOX and pseudoautosomal region 1

CONTEXT

Short stature has an incidence of three in 100 in children. Reliable molecular genetic testing may be crucial in the context of beneficial disease management. Deletions spanning or surrounding the SHOX gene account for a significant proportion of patients with idiopathic short stature (ISS) and allied disorders, such as Leri-Weill dyschondrosteosis.

OBJECTIVE

Several shortcomings of current strategies for copy number profiling of the SHOX region prompted us to develop an improved test for molecular diagnostics of the SHOX region.

DESIGN AND RESULTS

We introduced a quantitative PCR (qPCR)-based copy number profiling test, consisting of 11 amplicons targeting clinically relevant regions, i.e. the SHOX gene and regulatory regions. To ensure an optimal sensitivity and specificity, this test was validated in 32 controls and 18 probands with previously identified copy number changes. In addition, 152 probands with SHOX-associated phenotypes were screened, revealing 10 novel copy number changes.

CONCLUSION

This highly validated qPCR test supersedes other approaches for copy number screening of the SHOX region in terms of reliability, accuracy, and cost efficiency. In addition, another strong point is the fact that it can be easily implemented in any standard equipped molecular laboratory. Our qPCR-based test is highly recommended for molecular diagnostics of idiopathic short stature and allied disorders.

Cryptic intragenic deletion of the SHOX gene in a family with Léri-Weill dyschondrosteosis detected by Multiplex Ligation-Dependent Probe Amplification (MLPA)

LWD is associated to SHOX haploinsufficiency, in most cases, due to gene deletion. Generally FISH and microsatellite analysis are used to identify SHOX deletion. MLPA is a new method of detecting gene copy variation, allowing simultaneous analysis of several regions. Here we describe the presence of a SHOX intragenic deletion in a family with LWD, analyzed through different methodologies. Genomic DNA of 11 subjects from one family were studied by microsatellite analysis, direct sequencing and MLPA. FISH was performed in two affected individuals. Microsatellite analysis showed that all affected members shared the same haplotype suggesting the involvement of SHOX. MLPA detected an intragenic deletion involving exons IV-VIa, which was not detected by FISH and microsatellite analysis. In conclusion, the MLPA technique was proved to be the best solution on detecting this small deletion, it has the advantage of being less laborious also allowing the analysis of several regions simultaneously.

Short stature homeoboxcontaining gene and idiopathic short stature

The term idiopathic short stature (ISS) refers to patients who are short due to various unknown reasons. Although it is clear that multiple factors contribute to final height, genetic factors play a crucial role. Mutations of a human homeobox gene, short stature homeobox-containing (SHOX) gene, have been shown to be associated with the short stature phenotype in patients with Turner syndrome, most patients with Leri-Weill dyschondrosteosis and some cases of ISS. The prevalence of SHOX anomalies in subjects previously recognized as having ISS has been estimated at 2.4% in a large series of ISS individuals. This review focuses on the functional properties of the SHOX gene and its linkage to ISS.