Broadening the Spectrum of Ehlers Danlos Syndrome in Patients With Congenital Adrenal Hyperplasia

Genomic complexity and clinical significance of the RCCX locus

Nearly identical, repetitive elements in the genome contribute to the variability in genetic inheritance patterns, particularly in regions like the RCCX locus, where such repeats can lead to structural variations. In addition, during the formation of gametes as a result of meiosis, variants of loci with repetitive elements that do not code for the required proteins may occur. As a result, an individual with certain genetic rearrangements in this region may have an increased risk of developing a congenital disorder, particularly in cases where the non-functional allele is inherited dominantly. At the same time, there is still no routine or generally recognized diagnostic method to determine the sequence of the repetitive fragments. The functionally important RCCX locus consists of such repetitive fragments. The available knowledge about the genomic variants of the RCCX locus is fragmented, as there is no standardized method to determine its structure. It should be noted that in some structural variants of the RCCX locus, the sequence of protein-coding genes is disrupted, leading to the development of diseases such as congenital adrenal hyperplasia (CAH). Although genetic testing is generally accepted as a gold standard for CAH diagnosis, there are a myriad of strategies on which exact methods to use and in which order. The reason for this inconsistency lies in the complexity of the RCCX locus and the fact that each patient or carrier may have a highly individualized mutation or combination thereof. In this review, we have discussed all known methods that can be used to study the structure of the RCCX locus. As a result, optimal approaches are proposed for the diagnosis of the most common disease caused by lesions in the RCCX-CAH due to CYP21A2 deficiency.

Management of childbearing with hypermobile Ehlers-Danlos syndrome and hypermobility spectrum disorders: A scoping review and expert co-creation of evidence-based clinical guidelines

OBJECTIVE

To co-create expert guidelines for the management of pregnancy, birth, and postpartum recovery in the context of hypermobile Ehlers-Danlos syndrome (hEDS) and hypermobility spectrum disorders (HSD).

DESIGN

Scoping Review and Expert Co-creation.

SETTING

United Kingdom, United States of America, Canada, France, Sweden, Luxembourg, Germany, Italy, and the Netherlands.

SAMPLE

Co-creators (n = 15) included expertise from patients and clinicians from the International Consortium on the Ehlers-Danlos syndromes and Hypermobility Spectrum Disorders, facilitated by the Ehlers-Danlos Society.

METHODS

A scoping review using Embase, Medline, the Cochrane Central Register of Controlled Trials and CINHAL was conducted from May 2022 to September 2023. Articles were included if they reported primary research findings in relation to childbearing with hEDS/HSD, including case reports. No language limitations were placed on our search, and our team had the ability to translate and screen articles retrieved in English, French, Spanish, Italian, Russian, Swedish, Norwegian, Dutch, Danish, German, and Portuguese. The Mixed Methods Appraisal Tool was used to assess bias and quality appraise articles selected. The co-creation of guidelines was based on descriptive evidence synthesis along with practical and clinical experience supported by patient and public involvement activities.

RESULTS

Primary research studies (n = 14) and case studies (n = 21) including a total of 1,260,317 participants informed the co-creation of guidelines in four overarching categories: 1) Preconceptual: conception and screening, 2) Antenatal: risk assessment, management of miscarriage and termination of pregnancy, gastrointestinal issues and mobility, 3) Intrapartum: risk assessment, birth choices (mode of birth and intended place of birth), mobility in labor and anesthesia, and 4) Postpartum: wound healing, pelvic health, care of the newborn and infant feeding. Guidelines were also included in relation to pain management, mental health, nutrition and the common co-morbidities of postural orthostatic tachycardia syndrome, other forms of dysautonomia, and mast cell diseases.

CONCLUSIONS

There is limited high quality evidence available. Individualized strategies are proposed for the management of childbearing people with hEDS/HSD throughout pregnancy, birth, and the postpartum period. A multidisciplinary approach is advised to address frequently seen issues in this population such as tissue fragility, joint hypermobility, and pain, as well as common comorbidities, including dysautonomia and mast cell diseases.

Evaluating the efficacy of a long-read sequencing-based approach in the clinical diagnosis of neonatal congenital adrenocortical hyperplasia

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders predominantly characterized by impaired corticosteroid synthesis. Clinical phenotypes include hypoadrenocorticism, electrolyte disturbances, abnormal gonadal development, and short stature, of which severe hyponadrenocorticism and salt wasting can be life-threatening. Genetic analysis can help in the clinical diagnosis of CAH. However, the 21-OHD-causing gene CYP21A2 is arranged in tandem with the highly homologous CYP21A1P pseudogene, making it difficult to determine the exact genotypes using the traditional method of multiplex ligation-dependent probe amplification (MLPA) plus Sanger sequencing or next-generation sequencing (NGS). We applied a long-read sequencing-based approach termed comprehensive analysis of CAH (CACAH) to 48 newborns with CAH that were diagnosed by clinical features and the traditional MLPA plus Sanger sequencing method for retrospective analysis, to evaluate its efficacy in the clinical diagnosis of neonatal CAH. Compared with the MLPA plus Sanger sequencing method, CACAH showed 100 % consistency in detecting SNV/indel variants located in exons and exon-intron boundary regions of CAH-related genes. It can directly determine the cis-trans relationship without the need to analyze parental genotypes, which reduces the time to diagnosis. Moreover, CACAH was able to distinguish different CYP21A1P/CYP21A2 and TNXA/TNXB chimeras, and detect additional variants (CYP21A2 variants c.-121C > T, c.*13G > A, c.*52C > T, c.*440C > T, c.*443 T > C, and TNXB variants c.12463 + 2 T > C, c.12204 + 5G > A). We also identified the TNXB variant c.11435_11524 + 30del alone instead of as a part of the TNXA/TNXB-CH-1 chimera in two newborns, which might be introduced by gene conversion. All of these characteristics enabled clinicians to better explain the phenotype of subjects and manage them more effectively. CACAH has a great advantage over the traditional MLPA and Sanger sequencing methods, showing substantial potential in the genetic diagnosis and screening of neonatal CAH.

Clinical and molecular delineation of classical-like Ehlers-Danlos syndrome through a comprehensive next-generation sequencing-based screening system

Classical-like Ehlers-Danlos syndrome (clEDS) is an autosomal recessive disorder caused by complete absence of tenascin-X resulting from biallelic variation in TNXB. Thus far, 50 patients from 43 families with biallelic TNXB variants have been identified. Accurate detection of TNXB variants is challenging because of the presence of the pseudogene TNXA, which can undergo non-allelic homologous recombination. Therefore, we designed a genetic screening system that is performed using similar operations to other next-generation sequencing (NGS) panel analyses and can be applied to accurately detect TNXB variants and the recombination of TNXA-derived sequences into TNXB. Using this system, we identified biallelic TNXB variants in nine unrelated clEDS patients. TNXA-derived variations were found in >75% of the current cohort, comparable to previous reports. The current cohort generally exhibited similar clinical features to patients in previous reports, but had a higher frequency of gastrointestinal complications (e.g., perforation, diverticulitis, gastrointestinal bleeding, intestinal obstruction, rectal/anal prolapse, and gallstones). This report is the first to apply an NGS-based screening for TNXB variants and represents the third largest cohort of clEDS, highlighting the importance of increasing awareness of the risk of gastrointestinal complications.

Molecular basis and genetic testing strategies for diagnosing 21-hydroxylase deficiency, including CAH-X syndrome

Congenital adrenal hyperplasia (CAH) is a group of autosomally recessive disorders that result from impaired synthesis of glucocorticoid and mineralocorticoid. Most cases (~95%) are caused by mutations in the CYP21A2 gene, which encodes steroid 21-hydroxylase. CAH patients manifest a wide phenotypic spectrum according to their degree of residual enzyme activity. CYP21A2 and its pseudogene (CYP21A1P) are located 30 kb apart in the 6q21.3 region and share approximately 98% of their sequences in the coding region. Both genes are aligned in tandem with the C4, SKT19, and TNX genes, forming 2 segments of the RCCX modules that are arranged as STK19-C4A-CYP21A1P-TNXA-STK19B-C4B-CYP21A2-TNXB. The high sequence homology between the active gene and pseudogene leads to frequent microconversions and large rearrangements through intergenic recombination. The TNXB gene encodes an extracellular matrix glycoprotein, tenascin-X (TNX), and defects in TNXB cause Ehlers-Danlos syndrome. Deletions affecting both CYP21A2 and TNXB result in a contiguous gene deletion syndrome known as CAH-X syndrome. Because of the high homology between CYP21A2 and CYP21A1P, genetic testing for CAH should include an evaluation of copy number variations, as well as Sanger sequencing. Although it poses challenges for genetic testing, a large number of mutations and their associated phenotypes have been identified, which has helped to establish genotype-phenotype correlations. The genotype is helpful for guiding early treatment, predicting the clinical phenotype and prognosis, and providing genetic counseling. In particular, it can help ensure proper management of the potential complications of CAH-X syndrome, such as musculoskeletal and cardiac defects. This review focuses on the molecular pathophysiology and genetic diagnosis of 21-hydroxylase deficiency and highlights genetic testing strategies for CAH-X syndrome.

The pathogenic p.Gln319Ter variant is not causing congenital adrenal hyperplasia when inherited in one of the duplicated CYP21A2 genes

Objective

The study aimed to identify the pathogenic status of p.Gln319Ter (NM_000500.7: c.955C>T) variant when inherited in a single CYP21A2 gene (bimodular RCCX haplotype) and to discriminate between a non-causing congenital adrenal hyperplasia (CAH) allele when inherited in a duplicated and functional CYP21A2 gene context (trimodular RCCX haplotype).

Methods

38 females and 8 males with hyperandrogenemia, previously screened by sequencing and identified as carriers for the pathogenic p.Gln319Ter, were herein tested by multiplex ligation-dependent probe amplification (MLPA) and a real-time PCR Copy number Variation (CNV) assay.

Results

Both MLPA and real-time PCR CNV analyses confirmed a bimodular and pathogenic RCCX haplotype with a single CYP21A2 in 19/46 (41.30%) p.Gln319Ter carriers and who in parallel all shared elevated 17-OHP levels. The remaining 27 individuals that also carried the p.Gln319Ter exhibited low 17-OHP levels as a result of their carriership of a duplicated CYP21A2 with a trimodular RCCX haplotype. Interestingly, all of these individuals also carried in linkage disequilibrium with p.Gln319Ter two single nucleotide polymorphisms, the c.293-79G>A (rs114414746) in intron 2 and the c.*12C>T (rs150697472) in the 3'-UTR. Therefore, these variants can be used to distinguish between pathogenic and non-pathogenic genomic contexts of the c.955T (p.Gln319) in the genetic diagnosis of congenital adrenal hyperplasia (CAH).

Conclusion

The employed methodologies identified a considerable number of individuals with non-pathogenic p.Gln319Ter from the individuals that typically carry the pathogenic p.Gln319Ter in a single CYP21A2. Therefore, it is extremely important the detection of such haplotypes for the prenatal diagnosis, treatment and genetic counseling in patients with CAH.

Salt-wasting congenital adrenal hyperplasia phenotype as a result of the TNXA/TNXB chimera 1 (CAH-X CH-1) and the pathogenic IVS2-13A/C > G in CYP21A2 gene

BACKGROUND

Genetic diversity of mutations in the CYP21A2 gene is the main cause of the monogenic congenital adrenal hyperplasia (CAH) disorder. On chromosome 6p21.3, the CYP21A2 gene is partially overlapped by the TNXB gene, the two residing in tandem with their highly homologous corresponding pseudogenes (CYP21A1P and TNXA), which leads to recurrent homologous recombination.

METHODS AND RESULTS

In the present study, the genetic status of an ethnic Greek-Cypriot family, with a female neonate that was originally classified as male and manifested the salt-wasting (SW) form, is presented. Genetic defects in the CYP21A2 and TNXB genes were investigated by Sanger sequencing multiplex ligation-dependent probe amplification (MLPA) and a real-time PCR assay. The neonate carried in compound heterozygosity the TNXA/TNXB chimeric gene complex (termed CAH-X CH-1) that results in a contiguous CYP21A2 and TNXB deletion and in her second allele the pathogenic IVS2-13A/C > G (c.655A/C > G) in CYP21A2.

CONCLUSIONS

The classic SW-CAH due to 21-hydroxylase (21-OH) deficiency may result from various complex etiological mechanisms and, as such, can involve the formation of monoallelic TNXA/TNXB chimeras found in trans with other CYP21A2 pathogenic variants. This is a rare case of CAH due to 21-hydroxylase deficiency, which elucidates the role of the complex RCCX CNV structure in the development of the disease. Identification of the correct CAH genotypes for a given phenotype is of considerable value in assisting clinicians in prenatal diagnosis, appropriate treatment, and genetic counseling.

Congenital adrenal hyperplasia with a CYP21A2 deletion overlapping the tenascin-X gene: an atypical presentation

OBJECTIVES

Congenital Adrenal Hyperplasia (CAH) is a group of genetic diseases characterized by impaired cortisol biosynthesis. 95% of CAH cases result from mutation in the CYP21A2 gene encoding 21-hydroxilase. TNX-B gene partially overlaps CYP21A2 and encodes a matrix protein called Tenascin-X (TNX). Complete tenascin deficiency causes Enlers-Danlos syndrome (EDS). A mono allelic variant called CAH-X CH-1 was recently described, resulting from a CYP21A2 complete deletion that extends into the TNXB. This haploinsufficiency of TNX may be associated with a mild hypermobility form of EDS, as well as other connective tissue comorbidities such as hernia, cardiac defects and chronic arthralgia.

CASE PRESENTATION

We report four patients heterozygous for a CAH-X CH-1 allele that do not present clinical manifestations of the EDS.

CONCLUSIONS

All CAH patients, carriers of these TNXA/TNXB chimeras, should be evaluated for clinical manifestations related to connective tissue hypermobility, cardiac abnormalities and other EDS features, allowing for better clinical surveillance management.

Pseudogene TNXA Variants May Interfere with the Genetic Testing of CAH-X

CAH-X is a hypermobility-type Ehlers-Danlos syndrome connective tissue dysplasia affecting approximately 15% of patients with 21-hydroxylase deficiency (21-OHD) congenital adrenal hyperplasia (CAH) due to contiguous deletion of CYP21A2 and TNXB genes. The two most common genetic causes of CAH-X are CYP21A1P-TNXA/TNXB chimeras with pseudogene TNXA substitution for TNXB exons 35-44 (CAH-X CH-1) and TNXB exons 40-44 (CAH-X CH-2). A total of 45 subjects (40 families) from a cohort of 278 subjects (135 families of 21-OHD and 11 families of other conditions) were found to have excessive TNXB exon 40 copy number as measured by digital PCR. Here, we report that 42 subjects (37 families) had at least one copy of a TNXA variant allele carrying a TNXB exon 40 sequence, whose overall allele frequency was 10.3% (48/467). Most of the TNXA variant alleles were in cis with either a normal (22/48) or an In2G (12/48) CYP21A2 allele. There is potential interference with CAH-X molecular genetic testing based on copy number assessment, such as with digital PCR and multiplex ligation-dependent probe amplification, since this TNXA variant allele might mask a real copy number loss in TNXB exon 40. This interference most likely happens amongst genotypes of CAH-X CH-2 with an in trans normal or In2G CYP21A2 allele.

Copy-number analysis by base-level normalization: An intuitive visualization tool for evaluating copy number variations

Next-generation sequencing (NGS) facilitates comprehensive molecular analyses that help with diagnosing unsolved disorders. In addition to detecting single-nucleotide variations and small insertions/deletions, bioinformatics tools can identify copy number variations (CNVs) in NGS data, which improves the diagnostic yield. However, due to the possibility of false positives, subsequent confirmation tests are generally performed. Here, we introduce Copy-number Analysis by BAse-level NormAlization (CABANA), a visualization tool that allows users to intuitively identify candidate CNVs using the normalized single-base-level read depth calculated from NGS data. To demonstrate how CABANA works, NGS data were obtained from 474 patients with neuromuscular disorders. CNVs were screened using a conventional bioinformatics tool, ExomeDepth, and then we normalized and visualized those data at the single-base level using CABANA, followed by manual inspection by geneticists to filter out false positives and determine candidate CNVs. In doing so, we identified 31 candidate CNVs (7%) in 474 patients and subsequently confirmed all of them to be true using multiplex ligation-dependent probe amplification. The performance of CABANA was deemed acceptable by comparing its diagnostic yield with previous data about neuromuscular disorders. Despite some limitations, we expect CABANA to help researchers accurately identify CNVs and reduce the need for subsequent confirmation testing.

Prevalence of CAH-X Syndrome in Italian Patients with Congenital Adrenal Hyperplasia (CAH) Due to 21-Hydroxylase Deficiency

21-hydroxylase deficiency (21OHD), the most common form of congenital adrenal hyperplasia (CAH), is associated with pathogenic variants in CYP21A2 gene. The clinical form of the disease ranges from classic or severe to non-classic (NC) or mild late onset. The CYP21A2 gene is located on the long arm of chromosome 6, within the RCCX region, one of the most complex loci in the human genome. The 3′untranslated sequence of CYP21A2 exon 10 overlap the last exon of TNXB gene (these genes lie on the opposite strands of DNA and have the opposite transcriptional direction) that encodes an extracellular matrix glycoprotein tenascin-X (TNX). A recombination event between TNXB and its pseudogene TNXA causes a 30 kb deletion producing a chimeric TNXA/TNXB gene (CAH-X chimera) where both CYP21A2 and TNXB genes are impaired. This genetic condition characterizes a subset of patients with 21OHD who display the hypermobility phenotype of Ehlers–Danlos syndrome (hEDS) (CAH-X Syndrome). The aim of this study was to assess the prevalence of CAH-X syndrome in an Italian cohort of patients with 21OHD. At this purpose, 196 probands were recruited. Multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing were used to identify the CAH-X genotype. Twenty-one individuals showed the heterozygous continuous deletion involving the CYP21A2 and part of the TNXB gene. EDS-related clinical manifestations were identified in most patients carrying the CAH-X chimera. A CAH-X prevalence of 10.7% was estimated in our population.

CAH-X Syndrome: Genetic and Clinical Profile

The term CAH-X was coined to describe a subset of patients with 21-hydroxylase deficiency displaying a phenotype compatible with the hypermobility type of Ehlers Danlos syndrome. The genetic defect is due to the monoallelic presence of a CYP21A2 deletion extending into the gene encoding tenascin X (TNXB), a connective tissue extracellular matrix protein. The result is a chimeric TNXA/TNXB gene causing tenascin-X haploinsufficiency. The prevalence of CAH-X was estimated to be around 14-15% in large cohorts of patients with 21-hydroxylase deficiency. However, population studies are still scarce and the clinical picture of the syndrome has yet to be fully defined. In this review, we discuss the current knowledge regarding the genetic and clinical profile of the CAH-X syndrome.

Recurrent pneumothorax in a case of tenascin-X deficient Ehlers-Danlos syndrome: Broadening the phenotypic spectrum

The genomic region surrounding the Tenascin‐XB gene (TNXB) is a complex and duplicated region, with several pseudogenes that predispose to high rates of homologous recombination. Classical‐like Ehlers–Danlos syndrome (clEDS) is the result of tenascin‐X deficiency due to biallelic loss of function variants in the TNXB gene. Here we present a patient with clEDS and spontaneous pneumothorax, a feature not previously reported to be associated with this condition. Two inherited pathogenic/likely pathogenic variants were identified; a previously reported deletion resulting in a TNXA/TNXB chimeric gene and a novel frameshift variant. The Tenascin‐XB gene is well described in the literature to be associated with collagen metabolism, stabilization of the fibrillar‐collagen matrix and is expressed abundantly in the extracellular matrix. We propose that tenascin‐X deficiency is directly related to pneumothorax predisposition. This case expands the phenotypic spectrum of clEDS and highlights the challenges with molecular analysis and diagnosis

Congenital Adrenal Hyperplasia-Current Insights in Pathophysiology, Diagnostics, and Management

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders affecting cortisol biosynthesis. Reduced activity of an enzyme required for cortisol production leads to chronic overstimulation of the adrenal cortex and accumulation of precursors proximal to the blocked enzymatic step. The most common form of CAH is caused by steroid 21-hydroxylase deficiency due to mutations in CYP21A2. Since the last publication summarizing CAH in Endocrine Reviews in 2000, there have been numerous new developments. These include more detailed understanding of steroidogenic pathways, refinements in neonatal screening, improved diagnostic measurements utilizing chromatography and mass spectrometry coupled with steroid profiling, and improved genotyping methods. Clinical trials of alternative medications and modes of delivery have been recently completed or are under way. Genetic and cell-based treatments are being explored. A large body of data concerning long-term outcomes in patients affected by CAH, including psychosexual well-being, has been enhanced by the establishment of disease registries. This review provides the reader with current insights in CAH with special attention to these new developments.

Congenital Adrenal Hyperplasia and Ehlers-Danlos Syndrome

Congenital adrenal hyperplasia (CAH) secondary to 21-hydroxylase deficiency is an autosomal recessive disorder. The 21-hydroxylase enzyme P450c21 is encoded by the CYP21A2 gene located on chromosome 6p21.33 within the HLA major histocompatibility complex. This locus also contains the CYP21A1P, a non-functional pseudogene, that is highly homologous to the CYP21A2 gene. Other duplicated genes are C4A and C4B, that encode two isoforms of complement factor C4, the RP1 gene that encodes a serine/threonine protein kinase, and the TNXB gene that, encodes the extracellular matrix glycoprotein tenascin-X (TNX). TNX plays a role in collagen deposition by dermal fibroblasts and is expressed in the dermis of the skin and the connective tissue of the heart and skeletal muscle. During meiosis, misalignment may occur producing large gene deletions or gene conversion events resulting in chimeric genes. Chimeric recombination may occur between TNXB and TNXA. Three TNXA/TNXB chimeras have been described that differ in the junction site (CH1 to CH3) and result in a contiguous CYP21A2 and TNXB gene deletion, causing CAH-X syndrome. TNXB deficiency is associated with Ehlers Danlos syndrome (EDS). EDS comprises a clinically and genetically heterogeneous group of connective tissue disorders. As molecular analysis of the TNXB gene is challenging, the TNX-deficient type EDS is probably underdiagnosed. In this minireview, we will address the different strategies of molecular analysis of the TNXB-gene, as well as copy number variations and genetic status of TNXB in different cohorts. Furthermore, clinical features of EDS and clinical recommendations for long-term follow-up are discussed.

Ehlers-Danlos Syndromes, Joint Hypermobility and Hypermobility Spectrum Disorders

Ehlers-Danlos syndrome is an umbrella term for a clinically and genetically heterogeneous group of hereditary soft connective tissue disorders mainly featuring abnormal cutaneous texture (doughy/velvety, soft, thin, and/or variably hyperextensible skin), easy bruising, and joint hypermobility. Currently, musculoskeletal manifestations related to joint hypermobility are perceived as the most prevalent determinants of the quality of life of affected individuals. The 2017 International Classification of Ehlers-Danlos syndromes and related disorders identifies 13 clinical types due to deleterious variants in 19 different genes. Recent publications point out the possibility of a wider spectrum of conditions that may be considered members of the Ehlers-Danlos syndrome community. Most Ehlers-Danlos syndromes are due to inherited abnormalities affecting the biogenesis of fibrillar collagens and other components of the extracellular matrix. The introduction of next-generation sequencing technologies in the diagnostic setting fastened patients' classification and improved our knowledge on the phenotypic variability of many Ehlers-Danlos syndromes. This is impacting significantly patients' management and family counseling. At the same time, most individuals presenting with joint hypermobility and associated musculoskeletal manifestations still remain without a firm diagnosis, due to a too vague clinical presentation and/or the lack of an identifiable molecular biomarker. These individuals are currently defined with the term "hypermobility spectrum disorders". Hence, in parallel with a continuous update of the International Classification of Ehlers-Danlos syndromes, the scientific community is investing efforts in offering a more efficient framework for classifying and, hopefully, managing individuals with joint hypermobility.

Biomarkers for Ehlers-Danlos Syndromes: There Is a Role?

Ehlers-Danlos syndromes (EDS) are an inherited heterogeneous group of connective tissue disorders characterized by an abnormal collagen synthesis affecting skin, ligaments, joints, blood vessels, and other organs. It is one of the oldest known causes of bruising and bleeding, and it was described first by Hippocrates in 400 BC. In the last years, multiple gene variants involved in the pathogenesis of specific EDS subtypes have been identified; moreover, new clinical diagnostic criteria have been established. New classification models have also been studied in order to differentiate overlapping conditions. Moreover, EDS shares many characteristics with other similar disorders. Although distinguishing between these seemingly identical conditions is difficult, it is essential in ensuring proper patient care. Currently, there are many genetic and molecular studies underway to clarify the etiology of some variants of EDS. However, the genetic basis of the hypermobile type of EDS (hEDS) is still unknown. In this review, we focused on the study of two of the most common forms of EDS—classic and hypermobile—by trying to identify possible biomarkers that could be of great help to confirm patients’ diagnosis and their follow up.

Are patients with hypermobile Ehlers-Danlos syndrome or hypermobility spectrum disorder so different?

Diagnosing hypermobile Ehlers–Danlos syndrome (hEDS) remains challenging, despite new 2017 criteria. Patients not fulfilling these criteria are considered to have hypermobile spectrum disorder (HSD). Our first aim was to evaluate whether patients hEDS were more severely affected and had higher prevalence of extra-articular manifestations than HSD. Second aim was to compare their outcome after coordinated physical therapy. Patients fulfilling hEDS/HSD criteria were included in this real-life prospective cohort (November 2017/April 2019). They completed a 16-item Clinical Severity Score (CSS-16). We recorded bone involvement, neuropathic pain (DN4) and symptoms of mast cell disorders (MCAS) as extra-articular manifestations. After a standardized initial evaluation (T0), all patients were offered the same coordinated physical therapy, were followed-up at 6 months (T1) and at least 1 year later (T2), and were asked whether or not their condition had subjectively improved at T2. We included 97 patients (61 hEDS, 36 HSD). Median age was 40 (range 18–73); 92.7% were females. Three items from CSS-16 (pain, motricity problems, and bleeding) were significantly more severe with hEDS than HSD. Bone fragility, neuropathic pain and MCAS were equally prevalent. At T2 (20 months [range 18–26]) 54% of patients reported improvement (no difference between groups). On multivariable analysis, only family history of hypermobility predicted (favorable) outcome (p = 0.01). hEDS and HDS patients showed similar disease severity score except for pain, motricity problems and bleeding, and similar spectrum of extra-articular manifestations. Long-term improvement was observed in > 50% of patients in both groups. These results add weight to a clinical pragmatic proposition to consider hEDS/HSD as a single entity that requires the same treatments.

Ehlers-Danlos Syndrome: Molecular and Clinical Characterization of TNXA/TNXB Chimeras in Congenital Adrenal Hyperplasia

CONTEXT

The syndrome CAH-X is due to a contiguous gene deletion of CYP21A2 and TNXB resulting in TNXA/TNXB chimeras.

OBJECTIVE

To analyze TNXB gene status and to clinically evaluate the Ehlers-Danlos syndrome phenotype in a large cohort of Argentine congenital adrenal hyperplasia (CAH) patients to assess the prevalence of this condition in our population.

METHODS

TNXB gene analysis was performed in 66 nonrelated CAH patients that were carriers of the CYP21A2 gene deletion. A molecular strategy based on multiplex ligation-dependent probe amplification and Sanger sequencing analysis was developed allowing for the detection of different, previously described TNXA/TNXB chimeras, named CH1, CH2, and CH3. The main outcome measures were TNXB status of CAH patients that were carriers of the CYP21A2 deletion in the homozygous or heterozygous state.

RESULTS

TNXA/TNXB CH1 was found in 41%, CH2 in 29%, and CH3 in 1% of nonrelated alleles carrying the CYP21A2 deletion. Thus, overall 71% of alleles were found to carry a contiguous gene deletion. Sixty-seven percent of patients analyzed had a monoallelic form and 6% a biallelic form. All patients with the biallelic form had severe skin hyperextensibility and generalized joint hypermobility.

CONCLUSION

Based on the high frequency of TNXB alterations found in CYP21A2 deletion carrier alleles, we recommend evaluating TNXB status in these patients, and assessing connective tissue dysplasia, including cardiologic alterations in positive cases. The number of patients undergoing cardiological evaluation should be expanded to determine the incidence of structural and functional abnormalities in this cohort.

Latent TGF-β Activation Is a Hallmark of the Tenascin Family

Transforming growth factor-β (TGF-β) isoforms are secreted as inactive complexes formed through non-covalent interactions between bioactive TGF-β entities and their N-terminal pro-domains called latency-associated peptides (LAP). Extracellular activation of latent TGF-β within this complex is a crucial step in the regulation of TGF-β activity for tissue homeostasis and immune cell function. We previously showed that the matrix glycoprotein Tenascin-X (TN-X) interacted with the small latent TGF-β complex and triggered the activation of the latent cytokine into a bioactive TGF-β. This activation most likely occurs through a conformational change within the latent TGF-β complex and requires the C-terminal fibrinogen-like (FBG) domain of the glycoprotein. As the FBG-like domain is highly conserved among the Tenascin family members, we hypothesized that Tenascin-C (TN-C), Tenascin-R (TN-R) and Tenascin-W (TN-W) might share with TN-X the ability to regulate TGF-β bioavailability through their C-terminal domain. Here, we demonstrate that purified recombinant full-length Tenascins associate with the small latent TGF-β complex through their FBG-like domains. This association promotes activation of the latent cytokine and subsequent TGF-β cell responses in mammary epithelial cells, such as cytostasis and epithelial-to-mesenchymal transition (EMT). Considering the pleiotropic role of TGF-β in numerous physiological and pathological contexts, our data indicate a novel common function for the Tenascin family in the regulation of tissue homeostasis under healthy and pathological conditions.

Hypermobile Disorders and Their Effects on the Hip Joint

Hypermobility, or joint hyperlaxity, can result from inherited connective tissue disorders or from micro- or macrotrauma to a joint. The supraphysiologic motion of the hip joint results in capsuloligamentous damage, and these patients have a propensity to develop femoroacetabular impingement syndrome (FAIS) and labral injury. In this review, the recent literature evaluating the definitions, history, incidence, genetics, and histology of hypermobile disorders is investigated. We then review the clinical evaluation, natural history, and resulting instability for patients presenting with a hypermobile hip. Lastly, treatment options and outcomes will be highlighted.

Hypermobile Ehlers-Danlos syndromes: Complex phenotypes, challenging diagnoses, and poorly understood causes

The Ehlers-Danlos syndromes (EDS) are a group of heritable, connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. There is phenotypic and genetic variation among the 13 subtypes. The initial genetic findings on EDS were related to alterations in fibrillar collagen, but the elucidation of the molecular basis of many of the subtypes revealed several genes not involved in collagen biosynthesis or structure. However, the genetic basis of the hypermobile type of EDS (hEDS) is still unknown. hEDS is the most common type of EDS and involves generalized joint hypermobility, musculoskeletal manifestations, and mild skin involvement along with the presence of several comorbid conditions. Variability in the spectrum and severity of symptoms and progression of patient phenotype likely depend on age, gender, lifestyle, and expression domains of the EDS genes during development and postnatal life. In this review, we summarize the current molecular, genetic, epidemiologic, and pathogenetic findings related to EDS with a focus on the hypermobile type.

Genes and Pseudogenes: Complexity of the RCCX Locus and Disease

Copy Number Variations (CNVs) account for a large proportion of human genome and are a primary contributor to human phenotypic variation, in addition to being the molecular basis of a wide spectrum of disease. Multiallelic CNVs represent a considerable fraction of large CNVs and are strictly related to segmental duplications according to their prevalent duplicate alleles. RCCX CNV is a complex, multiallelic and tandem CNV located in the major histocompatibility complex (MHC) class III region. RCCX structure is typically defined by the copy number of a DNA segment containing a series of genes - the serine/threonine kinase 19 (STK19), the complement 4 (C4), the steroid 21-hydroxylase (CYP21), and the tenascin-X (TNX) - lie close to each other. In the Caucasian population, the most common RCCX haplotype (69%) consists of two segments containing the genes STK19-C4A-CYP21A1P-TNXA-STK19B-C4B-CYP21A2-TNXB, with a telomere-to-centromere orientation. Nonallelic homologous recombination (NAHR) plays a key role into the RCCX genetic diversity: unequal crossover facilitates large structural rearrangements and copy number changes, whereas gene conversion mediates relatively short sequence transfers. The results of these events increased the RCCX genetic diversity and are responsible of specific human diseases. This review provides an overview on RCCX complexity pointing out the molecular bases of Congenital Adrenal Hyperplasia (CAH) due to CYP21A2 deficiency, CAH-X Syndrome and disorders related to CNV of complement component C4.

A TNXB splice donor site variant as a cause of hypermobility type Ehlers-Danlos syndrome in patients with congenital adrenal hyperplasia

BACKGROUND

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is an autosomal recessive disease of steroidogenesis that affects 1 in 15,000. Approximately, 10% of the CAH population also suffer from CAH-X, a connective tissue dysplasia consistent with hypermobility type Ehlers-Danlos syndrome (EDS). Most patients with CAH-X carry a contiguous gene deletion involving CYP21A2 encoding 21-hydroxylase and TNXB encoding tenascin-X (TNX), but some are of unknown etiology.

METHODS

We conducted clinical evaluation and medical history review of EDS-related manifestations in subjects from two unrelated CAH families who carry a heterozygous TNXB c.12463+2T>C variant that alters the splice donor site of intron 42. A next generation sequencing (NGS) based EDS panel composed of 45 genes was performed for index patients from each family. TNX expression in patient skin biopsy tissues and dermal fibroblasts was assessed by qRT-PCR and Sanger sequencing.

RESULTS

All three evaluated CAH patients carrying the TNXB splice site variant had moderate EDS manifestations. An NGS panel excluded involvement of other known EDS-related variants. RNA assay on skin biopsies and dermal fibroblasts did not detect splicing errors in TNX mRNA; however, the removal of intron 42 was less efficient in the allele harboring the splice site variant as evidenced by the existence of a premature TNX RNA form, leading to an allele specific decrease in TNX mRNA.

CONCLUSIONS

Carrying a TNXB c.12463+2T>C variant at the intron 42 splice donor site causes an allele specific decrease in TNX expression, which can be associated with moderate EDS in CAH patients.

Pelvic Girdle Pain, Hypermobility Spectrum Disorder and Hypermobility-Type Ehlers-Danlos Syndrome: A Narrative Literature Review

Pelvic girdle pain (PGP) refers specifically to musculoskeletal pain localised to the pelvic ring and can be present at its anterior and/or posterior aspects. Causes such as trauma, infection and pregnancy have been well-established, while patients with hypermobile joints are at greater risk of developing PGP. Research exploring this association is limited and of varying quality. In the present study we report on the incidence, pathophysiology, diagnostic and treatment modalities for PGP in patients suffering from Hypermobility Spectrum Disorder (HSD) and Hypermobility-Type Ehlers-Danlos Syndrome (hEDS). Recommendations are made for clinical practice by elaborating on screening, diagnosis and management of such patients to provide a holistic approach to their care. It appears that this cohort of patients are at greater risk particularly of mental health issues. Moreover over, they may require a multidisciplinary approach for their management. Ongoing research is still required to expand our understanding of the relationship between PGP, HSD and hEDS by appropriately diagnosing patients using the latest updated terminologies and by conducting randomised control trials to compare outcomes of interventions using standardised patient reported outcome measures.

The Prevalence of the Chimeric TNXA/TNXB Gene and Clinical Symptoms of Ehlers-Danlos Syndrome with 21-Hydroxylase Deficiency

PURPOSE

Defects in both CYP21A2 and TNXB genes can cause congenital adrenal hyperplasia combined with hypermobility-type Ehlers-Danlos syndrome (EDS), which has recently been named CAH-X syndrome. The purpose of this study is to assess the prevalence of the chimeric TNXA/TNXB gene and clinical symptoms in a Chinese cohort with 21-hydroxylase deficiency (21-OHD).

METHODS

A total of 424 patients with 21-OHD who were genetically diagnosed were recruited for this study. Multiplex ligation-dependent probe amplification and sequencing were used to identify the CAH-X genotype. Clinical features of joints, skin, and other systems were evaluated in 125 patients.

RESULTS

Ninety-four of the 424 patients had a deletion on at least 1 allele of CYP21A2 and 59 of them harbored the heterozygotic TNXA/TNXB chimera. Frequencies of CAH-X CH-1, CH-2, and CH-3 were 8.2%, 3.1%, and 2.6%, respectively. The incidences of clinical features of EDS were 71.0% and 26.6% in patients with the chimeric TNXA/TNXB genes or without (P < .001). There were statistically significant differences in manifestations among articular (P < .001 in generalized hypermobility) and dermatologic features (P < .001 in hyperextensible skin, P = .015 in velvety skin and P = .033 in poor wound healing). The prevalence of generalized hypermobility was more common in CAH-X CH-2 or CH-3 than CH-1 patients (60% vs 20%, P = .028).

CONCLUSIONS

In summary, about 14% of patients with 21-OHD may have chimeric TNXA/TNXB gene mutations in our study and most of them showed EDS-related clinical symptoms. The correlation between CAH-X genotypes and clinical features in connective tissue, like joint or skin, needs to be further investigated.

Unusual Combination of MEN-1 and the Contiguous Gene Deletion Syndrome of CAH and Ehlers-Danlos Syndrome (CAH-X)

The contiguous gene deletion syndrome of congenital adrenal hyperplasia and Ehlers-Danlos syndrome, named CAH-X, is a rare entity that occurs because of a deletion of a chromosomal area containing 2 neighboring genes, TNXB and CYP21A. Here, we describe a patient from a consanguineous family in which coincidentally MEN-1 syndrome is associated with CAH-X, causing particular challenges explaining the phenotypic features of the patient. A 33-year-old man with salt-wasting congenital adrenal hyperplasia and classic-like Ehlers-Danlos syndrome presented with an adrenal crisis with a history of recurrent hypoglycemia, abdominal pain, and vomiting. He was found to have primary hyperparathyroidism, hyperprolactinemia, and pancreatic neuroendocrine tumors, as well as primary hypogonadism, large adrenal myelolipomas, and low bone mineral density. A bladder diverticulum was incidentally found. Genetic analysis revealed a heterozygous previously well-described MEN1 mutation (c.784-9G > A), a homozygous complete deletion of CYP21A2 (c.1-?_1488+? del), as well as a large deletion of the neighboring TNXB gene (c.11381-?_11524+?). The deletion includes the complete CYP21A2 gene and exons 35 through 44 of the TNXB gene. CGH array found 12% homozygosity over the whole genome. This rare case illustrates a complex clinical scenario with some initial diagnostic challenges.

Classical-like Ehlers-Danlos syndrome: a clinical description of 20 newly identified individuals with evidence of tissue fragility

PURPOSE

Currently, 31 patients with classical-like EDS (clEDS) due to tenascin-X deficiency have been reported in the literature. We report on the clinical and molecular characteristics of 20 additional patients with clEDS to expand knowledge and to enable improved management of this rare genetic disorder.

METHODS

Patients diagnosed with clEDS by the national EDS service in the UK (n = 21) and abroad (n = 1) were asked for consent for publication of their clinical and molecular data.

RESULTS

Of 22 patients, 20 consented. All patients had typical features of clEDS: joint hypermobility, easy bruising, and skin hyperextensibility without atrophic scars. Importantly, 3/20 patients experienced gastrointestinal complications consisting of small or large bowel ruptures and one esophageal rupture. Other notable observations included two separate occurrences of spontaneous compartment syndrome, suspicion of nonaccidental injury due to significant bruising, and significant clinical variability regarding the debilitating effect of joint dislocations.

CONCLUSIONS

We propose a predisposition to tissue fragility, particularly of the gastrointestinal tract in patients with clEDS. As such, clinical and molecular confirmation of this diagnosis is essential. It is recommended to follow up these patients closely to understand the natural history to develop better recommendations for management.

The Relationship Between Hypermobile Ehlers-Danlos Syndrome (hEDS), Postural Orthostatic Tachycardia Syndrome (POTS), and Mast Cell Activation Syndrome (MCAS)

In recent years, an association between hypermobile Ehlers-Danlos syndrome (hEDS), mast cell activation syndrome (MCAS), and postural orthostatic tachycardia syndrome (POTS) has garnered attention and patients are increasingly presenting with this triad. However, a real relationship between these entities is unclear due to a lack of scientific validity. We conducted an extensive review of the literature using two different search strategies. A narrower strategy included 88 searches of various combinations of terms for each of the three conditions, yielding 19 unique papers. A broader search included 136 searches of various combinations of terms but included all forms of EDS and yielded 40 unique papers. Of these, only four and nine papers from the narrower and broader search strategies were original research articles. None of these papers resulted from a combination of the search terms for the three conditions. All three clinical entities are controversial in either existence or pathogenesis. MCAS is a poorly defined clinical entity, and many studies do not adhere to the proposed criteria when establishing the diagnosis. Patients previously diagnosed with EDS hypermobility type may not meet the new, stricter criteria for hEDS but may for a less severe hypermobility spectrum disorder (HSD). The pathophysiology of POTS is still unclear. An evidence-based, common pathophysiologic mechanism between any of the two, much less all three conditions, has yet to be described. Our review of the literature shows that current evidence is lacking on the existence of MCAS or hEDS as separate or significant clinical entities. Studies proposing a relationship between the three clinical entities are either biased or based on outdated criteria. The reason behind the purported association of these entities stems from an overlapping pool of vague, subjective symptoms, which is inadequate evidence to conclude that any such relationship exists.

Novel TNXB Variants in Two Italian Patients with Classical-Like Ehlers-Danlos Syndrome

TNXB-related classical-like Ehlers-Danlos syndrome (TNXB-clEDS) is an ultrarare type of Ehlers-Danlos syndrome due to biallelic null variants in TNXB, encoding tenascin-X. Less than 30 individuals have been reported to date, mostly of Dutch origin and showing a phenotype resembling classical Ehlers-Danlos syndrome without atrophic scarring. TNXB-clEDS is likely underdiagnosed due to the complex structure of the TNXB locus, a fact that complicates diagnostic molecular testing. Here, we report two unrelated Italian women with TNXB-clEDS due to compound heterozygosity for null alleles in TNXB. Both presented soft and hyperextensible skin, generalized joint hypermobility and related musculoskeletal complications, and chronic constipation. In addition, individual 1 showed progressive finger contractures and shortened metatarsals, while individual 2 manifested recurrent subconjunctival hemorrhages and an event of spontaneous rupture of the brachial vein. Molecular testing found the two previously unreported c.8278C > T p.(Gln2760*) and the c.(2358 + 1_2359 − 1)_(2779 + 1_2780 − 1)del variants in Individual 1, and the novel c.1150dupG p.(Glu384Glyfs*57) and the recurrent c.11435_11524+30del variants in Individual 2. mRNA analysis confirmed that the c.(2358 + 1_2359 − 1)_(2779 + 1_2780 − 1)del variant causes a frameshift leading to a predicted truncated protein [p.(Thr787Glyfs*40)]. This study refines the phenotype recently delineated in association with biallelic null alleles in TNXB, and adds three novel variants to its mutational repertoire. Unusual digital anomalies seem confirmed as possibly peculiar of TNXB-clEDS, while vascular fragility could be more than a chance association also in this Ehlers-Danlos syndrome type.

Measurement of serum tenascin-X in patients with congenital adrenal hyperplasia at risk for Ehlers-Danlos contiguous gene deletion syndrome CAH-X

Objective

Approximately 10% of patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency carry a mutation that disrupts CYP21A2 and the flanking TNXB gene resulting in CAH-X, a contiguous gene deletion syndrome. TNXB encodes tenascin-X (TNX), an extracellular matrix glycoprotein that plays an important role in collagen organization. TNXB impairment is associated with Ehlers–Danlos syndrome. Symptoms include joint hypermobility, hernias and cardiac defects. We measured serum TNX using an antibody targeting the amino-terminal of the TNX protein in 161 subjects, including extensively genotyped and phenotyped CAH patients, their relatives, and healthy controls.

Results

We evaluated the potential of serum TNX as a screening tool for CAH-X. CAH-X patients, especially haploinsufficient patients carrying the TNXA-TNXB chimeric gene CAH-X-CH-1 showed reduced TNX levels compared to controls (P < 0.05). TNX levels were similar in all subjects carrying a TNXB mutation. However, CAH patients who did not harbor a TNXB mutation also had reduced TNX compared to controls (P < 0.001). Thus, measuring serum TNX is not an effective screen for CAH-X amongst patients with CAH. TNXB genotyping is recommended for CAH patients who have symptoms of a connective tissue disorder. Epigenetic factors that influence TNX expression require further study.

46,XX DSD due to Androgen Excess in Monogenic Disorders of Steroidogenesis: Genetic, Biochemical, and Clinical Features

The term 'differences of sex development' (DSD) refers to a group of congenital conditions that are associated with atypical development of chromosomal, gonadal, or anatomical sex. Disorders of steroidogenesis comprise autosomal recessive conditions that affect adrenal and gonadal enzymes and are responsible for some conditions of 46,XX DSD where hyperandrogenism interferes with chromosomal and gonadal sex development. Congenital adrenal hyperplasias (CAHs) are disorders of steroidogenesis that mainly involve the adrenals (21-hydroxylase and 11-hydroxylase deficiencies) and sometimes the gonads (3-beta-hydroxysteroidodehydrogenase and P450-oxidoreductase); in contrast, aromatase deficiency mainly involves the steroidogenetic activity of the gonads. This review describes the main genetic, biochemical, and clinical features that apply to the abovementioned conditions. The activities of the steroidogenetic enzymes are modulated by post-translational modifications and cofactors, particularly electron-donating redox partners. The incidences of the rare forms of CAH vary with ethnicity and geography. The elucidation of the precise roles of these enzymes and cofactors has been significantly facilitated by the identification of the genetic bases of rare disorders of steroidogenesis. Understanding steroidogenesis is important to our comprehension of differences in sexual development and other processes that are related to human reproduction and fertility, particularly those that involve androgen excess as consequence of their impairment.

Cellular and Molecular Mechanisms in the Pathogenesis of Classical, Vascular, and Hypermobile Ehlers‒Danlos Syndromes

The Ehlers‒Danlos syndromes (EDS) constitute a heterogenous group of connective tissue disorders characterized by joint hypermobility, skin abnormalities, and vascular fragility. The latest nosology recognizes 13 types caused by pathogenic variants in genes encoding collagens and other molecules involved in collagen processing and extracellular matrix (ECM) biology. Classical (cEDS), vascular (vEDS), and hypermobile (hEDS) EDS are the most frequent types. cEDS and vEDS are caused respectively by defects in collagen V and collagen III, whereas the molecular basis of hEDS is unknown. For these disorders, the molecular pathology remains poorly studied. Herein, we review, expand, and compare our previous transcriptome and protein studies on dermal fibroblasts from cEDS, vEDS, and hEDS patients, offering insights and perspectives in their molecular mechanisms. These cells, though sharing a pathological ECM remodeling, show differences in the underlying pathomechanisms. In cEDS and vEDS fibroblasts, key processes such as collagen biosynthesis/processing, protein folding quality control, endoplasmic reticulum homeostasis, autophagy, and wound healing are perturbed. In hEDS cells, gene expression changes related to cell-matrix interactions, inflammatory/pain responses, and acquisition of an in vitro pro-inflammatory myofibroblast-like phenotype may contribute to the complex pathogenesis of the disorder. Finally, emerging findings from miRNA profiling of hEDS fibroblasts are discussed to add some novel biological aspects about hEDS etiopathogenesis.

High-Throughput Screening for CYP21A1P-TNXA/TNXB Chimeric Genes Responsible for Ehlers-Danlos Syndrome in Patients with Congenital Adrenal Hyperplasia

Many patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency have CAH-X syndrome, a connective tissue dysplasia consistent with hypermobility-type Ehlers-Danlos syndrome due to a contiguous gene deletion involving the adjacent CYP21A2 and TNXB genes. CAH-X syndrome is caused by carrying CYP21A1P-TNXA/TNXB chimeric genes [CAH-X chimera 1 (CH-1) and chimera 2 (CH-2)] on one or more alleles. Genetic analysis is cumbersome due to pseudogene interference. We developed a PCR-based CAH-X high-throughput screening method to assess the copy numbers of TNXB exons 35 and 40; this method is amenable to either real-time quantitative PCR or droplet digital PCR (ddPCR). The assay was validated in a cohort of 278 subjects from 146 unrelated CAH families. Results were confirmed by a validated Sanger sequencing platform. A total of 44 CAH-X-positive calls were made, with 42 (26 CH-1 and 16 CH-2) confirmed. The assay had 100% sensitivity (42 true/42 positives), 99.2% specificity (234 true/236 negatives), and an overall 99.3% accuracy (276/278). Calls made by real-time quantitative PCR and ddPCR were consistent (100%), and ddPCR offered easier data interpretation. The CAH-X prevalence was 15.6% (21/135 probands), higher than the previously estimated 8.5%, and was particularly high (29.2% or 21/72) in those with a 30-Kb deletion. This assay is suitable for high-throughput CAH-X screening, especially in subjects testing positive for CAH in neonatal screening.

Revisiting the association of HLA alleles and haplotypes with CYP21A2 mutations in a large cohort of patients with congenital adrenal hyperplasia

The CYP21A2 gene encoding 21‑hydroxylase is on chromosome 6p21.3 within the human leukocyte antigen (HLA) class III major histocompatibility complex and an association between congenital adrenal hyperplasia (CAH) due to 21‑hydroxylase deficiency and HLA class I and II alleles has been shown in genetically isolated populations. One-third of CAH causing alleles are 30-kb deletions due to homologous recombination events between active and pseudogenes resulting in chimeric genes. The aim of this study was to re-visit the association between the CYP21A2 variants and HLA polymorphisms in a large ethnically diverse cohort of patients with CAH who underwent comprehensive CYP21A2 genotyping, including specification of chimeric gene subtypes (CAH CH-1 through CH-9 of CYP21A1P/CYP21A2 chimeras; CAH-X CH-1 through CH-3 of TNXA/TNXB chimeras) in alleles with 30-kb deletions. The study population included 201 patients (86 males, 115 females, age 3-75 years) with CAH due to 21‑hydroxylase deficiency (159 classic, 42 nonclassic) and 194 parents. Based on the availability of parental genotype, we determined the haplotypes of CYP21A2 mutations and HLA types in 95 probands (190 alleles). Five prevalent haplotype associations were found: p.V281L and B*14-C*08 (P < 0.0001); p.I172N and DQB1*03 (P = 0.035); and of the chimeric genes caused by 30-kb deletions: CH-1 and A*03 (P = 0.033); CH-5 and C*06-DRB1*07 (P < 0.0001); and CAH-X CH-1 and DQB1*03 (P = 0.004). Our findings show that a number of associations between HLA alleles and haplotypes and CYP21A2 mutations, including large 30-kb deletions, exist commonly across ethnicities. These HLA associations may have clinical implications for patients with CAH and may provide insight into the genetics of this highly complex region of the human genome.

Complement component 4 variations may influence psychopathology risk in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

CYP21A2 defects result in congenital adrenal hyperplasia (CAH), an autosomal recessive disorder characterized by impaired adrenal steroidogenesis. CYP21A2 lies within the major histocompatibility complex in an area of the genome highly susceptible to genetic variation. Alterations in the neighboring complement component 4 isotypes C4A and C4B have been associated with psychiatric and autoimmune disease. The purpose of this study was to evaluate C4A and C4B in patients with CAH in relation to CYP21A2 genotype and psychiatric and autoimmune comorbidity. We determined the copy numbers of C4A and C4B in 145 patients with CAH (median age: 15.5 years, IQR: 16.8) and 108 carrier relatives (median age: 41.5 years, IQR: 12.0) and evaluated serum C4 concentrations. Comorbidity was determined by medical record review. Only 30% of subjects had the expected two copies each of the two C4 genes. C4B copy number determined total C4 copy number and serum C4 concentration, negatively correlated with carriership of a 30-kb deletion (P < 10^- 5), and positively correlated with carriership of p.V281L (P < 10^- 5). High C4A copy number (≥ 3) was associated with increased risk of having an externalizing psychiatric condition (relative risk: 2.67, 95% CI: 1.03-6.89, P = 0.04). No association was found between C4 copy number and autoimmune disease. Mutation-specific C4 structural variations commonly occur in patients with CAH and may have important clinical consequences, including increased risk of psychiatric morbidity. Trial registration NCT00250159 (November 7, 2005).

Updates in Clinical and Genetics Aspects of Hypermobile Ehlers Danlos Syndrome

Efforts on recognition, diagnosis, and management of the presumed, most common connective tissue disorder hypermobile Ehlers-Danlos syndrome have been an ongoing challenge, even decades after the description of this condition. A recent international consortium proposed a revised Ehlers-Danlos syndrome classification, an update much needed since Villefranche nosology, in 1998. Hypermobile Ehlers-Danlos syndrome is the only subtype in these groups of syndromes with no known genetic cause(s). This effort brought significant attention to this often underappreciated condition. This review provides an update of the clinical and genetic aspects of hypermobile Ehlers-Danlos syndrome for clinicians and researchers.

An overview of inborn errors of metabolism manifesting with primary adrenal insufficiency

Primary adrenal insufficiency (PAI) results from an inability to produce adequate amounts of steroid hormones from the adrenal cortex. The most common causes of PAI are autoimmune adrenalitis (Addison's disease), infectious diseases, adrenalectomy, neoplasia, medications, and various rare genetic syndromes and inborn errors of metabolism that typically present in childhood although late-onset presentations are becoming increasingly recognized. The prevalence of PAI in Western countries is approximately 140 cases per million, with an incidence of 4 per 1,000,000 per year. Several pitfalls in the genetic diagnosis of patients with PAI exist. In this review, we provide an in-depth discussion and overview on the inborn errors of metabolism manifesting with PAI, including genetic diagnosis, genotype-phenotype relationships and counseling of patients and their families with a focus on various enzymatic deficiencies of steroidogenesis.

Tenascin-X, Congenital Adrenal Hyperplasia, and the CAH-X Syndrome

Mutations of the CYP21A2 gene encoding adrenal 21-hydroxylase cause congenital adrenal hyperplasia (CAH). The CYP21A2 gene is partially overlapped by the TNXB gene, which encodes an extracellular matrix protein called Tenascin-X (TNX). Mutations affecting both alleles of TNXB cause a severe, autosomal recessive form of Ehlers-Danlos syndrome (EDS). Rarely, patients with severe, salt-wasting CAH have deletions of CYP21A2 that extend into TNXB, resulting in a "contiguous gene syndrome" consisting of CAH and EDS. Heterozygosity for TNXB mutations causing haploinsufficiency of TNX may be associated with the mild "hypermobility form" of EDS, which principally affects small and large joints. Studies of patients with salt-wasting CAH found that up to 10% had clinical features of EDS, associated joint hypermobility, haploinsufficiency of TNX and heterozygosity for TNXB mutations, now called "CAH-X." These patients have joint hypermobility and a spectrum of other comorbidities associated with their connective tissue disorder, including chronic arthralgia, joint subluxations, hernias, and cardiac defects. Other disorders are beginning to be associated with TNX deficiency, including familial vesicoureteral reflux and neurologic disorders. Further work is needed to delineate the full spectrum of TNX-deficient disorders, with and without associated CAH.

Congenital adrenal hyperplasia

Congenital adrenal hyperplasia is a group of autosomal recessive disorders encompassing enzyme deficiencies in the adrenal steroidogenesis pathway that lead to impaired cortisol biosynthesis. Depending on the type and severity of steroid block, patients can have various alterations in glucocorticoid, mineralocorticoid, and sex steroid production that require hormone replacement therapy. Presentations vary from neonatal salt wasting and atypical genitalia, to adult presentation of hirsutism and irregular menses. Screening of neonates with elevated 17-hydroxyprogesterone concentrations for classic (severe) 21-hydroxylase deficiency, the most common type of congenital adrenal hyperplasia, is in place in many countries, however cosyntropin stimulation testing might be needed to confirm the diagnosis or establish non-classic (milder) subtypes. Challenges in the treatment of congenital adrenal hyperplasia include avoidance of glucocorticoid overtreatment and control of sex hormone imbalances. Long-term complications include abnormal growth and development, adverse effects on bone and the cardiovascular system, and infertility. Novel treatments aim to reduce glucocorticoid exposure, improve excess hormone control, and mimic physiological hormone patterns.

The Ehlers-Danlos syndromes, rare types

The Ehlers-Danlos syndromes comprise a clinically and genetically heterogeneous group of heritable connective tissue disorders, which are characterized by joint hypermobility, skin hyperextensibility, and tissue friability. In the Villefranche Nosology, six subtypes were recognized: The classical, hypermobile, vascular, kyphoscoliotic, arthrochalasis, and dermatosparaxis subtypes of EDS. Except for the hypermobile subtype, defects had been identified in fibrillar collagens or in collagen-modifying enzymes. Since 1997, a whole spectrum of novel, clinically overlapping, rare EDS-variants have been delineated and genetic defects have been identified in an array of other extracellular matrix genes. Advances in molecular testing have made it possible to now identify the causative mutation for many patients presenting these phenotypes. The aim of this literature review is to summarize the current knowledge on the rare EDS subtypes and highlight areas for future research. © 2017 Wiley Periodicals, Inc.

Genetics of Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders due to single-gene defects in the various enzymes required for cortisol biosynthesis. CAH represents a continuous phenotypic spectrum with more than 95% of all cases caused by 21-hydroxylase deficiency. Genotyping is an important tool in confirming the diagnosis or carrier state, provides prognostic information on disease severity, and is essential for genetic counseling. In this article, the authors provide an in-depth discussion on the genetics of CAH, including genetic diagnosis, molecular analysis, genotype-phenotype relationships, and counseling of patients and their families.

Hypermobile Ehlers-Danlos syndrome (a.k.a. Ehlers-Danlos syndrome Type III and Ehlers-Danlos syndrome hypermobility type): Clinical description and natural history

The hypermobile type of Ehlers-Danlos syndrome (hEDS) is likely the most common hereditary disorder of connective tissue. It has been described largely in those with musculoskeletal complaints including joint hypermobility, joint subluxations/dislocations, as well as skin and soft tissue manifestations. Many patients report activity-related pain and some go on to have daily pain. Two undifferentiated syndromes have been used to describe these manifestations-joint hypermobility syndrome and hEDS. Both are clinical diagnoses in the absence of other causation. Current medical literature further complicates differentiation and describes multiple associated symptoms and disorders. The current EDS nosology combines these two entities into the hypermobile type of EDS. Herein, we review and summarize the literature as a better clinical description of this type of connective tissue disorder. © 2017 Wiley Periodicals, Inc.

Recognizing the tenascin-X deficient type of Ehlers-Danlos syndrome: a cross-sectional study in 17 patients

The tenascin-X (TNX) deficient type Ehlers-Danlos syndrome (EDS) is similar to the classical type of EDS. Because of the limited awareness among geneticists and the challenge of the molecular analysis of the TNXB gene, the TNX-deficient type EDS is probably to be under diagnosed. We therefore performed an observational, cross-sectional study. History and physical examination were performed. Results of serum TNX measurements were collected and mutation analysis was performed by a combination of next-generation sequencing (NGS), Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). Included were 17 patients of 11 families with autosomal recessive inheritance and childhood onset. All patients had hyperextensible skin without atrophic scarring. Hypermobility of the joints was observed in 16 of 17 patients. Deformities of the hands and feet were observed frequently. TNX serum level was tested and absent in 11 patients (seven families). Genetic testing was performed in all families; 12 different mutations were detected, most of which are suspected to lead to non-sense mRNA mediated decay. In short, patients with the TNX-deficient type EDS typically have generalized joint hypermobility, skin hyperextensibility and easy bruising. In contrast to the classical type, the inheritance pattern is autosomal recessive and atrophic scarring is absent. Molecular analysis of TNXB in a diagnostic setting is challenging.

Ehlers-Danlos Syndrome Caused by Biallelic TNXB Variants in Patients with Congenital Adrenal Hyperplasia

Some variants that cause autosomal-recessive congenital adrenal hyperplasia (CAH) also cause hypermobility type Ehlers-Danlos syndrome (EDS) due to the monoallelic presence of a chimera disrupting two flanking genes: CYP21A2, encoding 21-hydroxylase, necessary for cortisol and aldosterone biosynthesis, and TNXB, encoding tenascin-X, an extracellular matrix protein. Two types of CAH tenascin-X (CAH-X) chimeras have been described with a total deletion of CYP21A2 and characteristic TNXB variants. CAH-X CH-1 has a TNXB exon 35 120-bp deletion resulting in haploinsufficiency, and CAH-X CH-2 has a TNXB exon 40 c.12174C>G (p.Cys4058Trp) variant resulting in a dominant-negative effect. We present here three patients with biallelic CAH-X and identify a novel dominant-negative chimera termed CAH-X CH-3. Compared with monoallelic CAH-X, biallelic CAH-X results in a more severe phenotype with skin features characteristic of classical EDS. We present evidence for disrupted tenascin-X function and computational data linking the type of TNXB variant to disease severity.

Genetics of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the deficiency of one of four steroidogenic enzymes involved in cortisol biosynthesis or in the electron donor enzyme P450 oxidoreductase (POR) that serves as electron donor to steroidogenic cytochrome P450 (CYP) type II enzymes. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity. Defects of steroid 21-hydroxylase (CYP21A2) and 11beta-hydroxylase (CYP11B1) only affect adrenal steroidogenesis, whereas 17alpha-hydroxylase (CYP17A1) and 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency also impact on gonadal steroid biosynthesis. Inactivating POR gene mutations are the cause of CAH manifesting with apparent combined CYP17A1-CYP21A2 deficiency. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant: skeletal malformations and severe genital ambiguity in both sexes.