Flemish network on rare connective tissue diseases (CTD): patient pathways in systemic sclerosis. First steps taken.

Despite the low prevalence of each rare disease, the total burden is high. Patients with rare diseases encounter numerous barriers, including delayed diagnosis and limited access to high-quality treatments. In order to tackle these challenges, the European Commission launched the European Reference Networks (ERNs), cross-border networks of healthcare providers and patients representatives. In parallel, the aims and structure of these ERNs were translated at the federal and regional levels, resulting in the creation of the Flemish Network of Rare Diseases. In line with the mission of the ERNs and to ensure equal access to care, we describe as first patient pathways for systemic sclerosis (SSc), as a pilot model for other rare connective and musculoskeletal diseases. Consensus was reached on following key messages: 1. Patients with SSc should have multidisciplinary clinical and investigational evaluations in a tertiary reference expert centre at baseline, and subsequently every three to 5 years. Intermediately, a yearly clinical evaluation should be provided in the reference centre, whilst SSc technical evaluations are permissionably executed in a centre that follows SSc-specific clinical practice guidelines. In between, monitoring can take place in secondary care units, under the condition that qualitative examinations and care including interactive multidisciplinary consultations can be provided. 2. Patients with early diffuse cutaneous SSc, (progressive) interstitial lung disease and/or pulmonary arterial hypertension should undergo regular evaluations in specialised tertiary care reference institutions. 3. Monitoring of patients with progressive interstitial lung disease and/or pulmonary (arterial) hypertension will be done in agreement with experts of ERN LUNG.

Higher fracture prevalence and smaller bone size in patients with hEDS/HSD-a prospective cohort study.

Increased fracture risk in patients with Ehlers-Danlos syndromes has been reported, but the reasons for it are incompletely understood. We aimed to investigate possible determinants of this increased risk and found that hEDS/HSD patients present with a cortical bone size deficit compared with control subjects, possibly related to lower mechanical loading. INTRODUCTION: The Ehlers-Danlos syndromes (EDS) comprise a group of heritable connective tissue disorders caused by defects in the biosynthesis, secretion, and/or organization of fibrillar collagens which might impair bone strength. Our aim was to compare fracture prevalence, volumetric and areal bone mineral density (BMD), bone geometry, muscle size and the muscle-bone interaction, body composition and longitudinal changes therein between patients with hypermobile EDS (hEDS) or hypermobility spectrum disorder (HSD), and healthy control subjects. METHODS: Cross-sectional data comprised 39 female hEDS/HSD patients (age 41 ± 11 years) and 43 age-matched controls. After 8 years, 27 hEDS/HSD and 17 control subjects were re-evaluated. Tibial trabecular and cortical volumetric BMD, bone mineral content (BMC), cortical bone geometry, and lower leg muscle cross-sectional area (CSA) were measured using pQCT. Body composition, areal BMD, and BMC were determined by DXA. RESULTS: At baseline, patients with hEDS/HSD presented with a smaller cortical bone area, smaller cortical thickness and muscle CSA, and a higher fracture prevalence than control subjects (all p < 0.05). No differences in areal or volumetric BMD were found. Longitudinally, muscle CSA decreased in both groups and muscle density decreased in the hEDS/HSD group (p < 0.001) whereas all bone parameters remained unchanged. CONCLUSION: hEDS/HSD patients have a cortical bone size deficit compared with controls, possibly contributing to their increased fracture risk. They presented with decreased muscle CSA but normal bone/muscle area ratio, suggesting that this bone size deficit is likely secondary to decreased mechanical loading. Further, there were no arguments for accelerated bone loss in hEDS/HSD subjects.

Zebrafish Collagen Type I: Molecular and Biochemical Characterization of the Major Structural Protein in Bone and Skin.

Over the last years the zebrafish imposed itself as a powerful model to study skeletal diseases, but a limit to its use is the poor characterization of collagen type I, the most abundant protein in bone and skin. In tetrapods collagen type I is a trimer mainly composed of two α1 chains and one α2 chain, encoded by COL1A1 and COL1A2 genes, respectively. In contrast, in zebrafish three type I collagen genes exist, col1a1a, col1a1b and col1a2 coding for α1(I), α3(I) and α2(I) chains. During embryonic and larval development the three collagen type I genes showed a similar spatio-temporal expression pattern, indicating their co-regulation and interdependence at these stages. In both embryonic and adult tissues, the presence of the three α(I) chains was demonstrated, although in embryos α1(I) was present in two distinct glycosylated states, suggesting a developmental-specific collagen composition. Even though in adult bone, skin and scales equal amounts of α1(I), α3(I) and α2(I) chains are present, the presented data suggest a tissue-specific stoichiometry and/or post-translational modification status for collagen type I. In conclusion, this data will be useful to properly interpret results and insights gained from zebrafish models of skeletal diseases.

The Ehlers-Danlos syndrome, a disorder with many faces.

The Ehlers-Danlos syndromes (EDSs) comprise a heterogeneous group of diseases, characterized by fragility of the soft connective tissues and widespread manifestations in skin, ligaments, joints, blood vessels and internal organs. The clinical spectrum varies from mild skin and joint hyperlaxity to severe physical disability and life-threatening vascular complications. The current Villefranche classification recognizes six subtypes, most of which are linked to mutations in genes encoding fibrillar collagens or enzymes involved in post-translational modification of these proteins. Mutations in type V and type III collagen cause classic or vascular EDS respectively, while mutations involving the processing of type I collagen are involved in the kyphoscoliosis, arthrochalasis and dermatosparaxis type of EDS. Establishing the correct EDS subtype has important implications for genetic counseling and management and is supported by specific biochemical and molecular investigations. Over the last years, several new EDS variants have been characterized which call for a refinement of the Villefranche classification. Moreover, the study of these diseases has brought new insights into the molecular pathogenesis of EDS by implicating genetic defects in the biosynthesis of other extracellular matrix (ECM) molecules, such as proteoglycans and tenascin-X, or genetic defects in molecules involved in intracellular trafficking, secretion and assembly of ECM proteins.

Superior mesenteric artery aneurysm in a 9-year-old boy with classical Ehlers-Danlos syndrome.

A 9-year-old boy with the classical type of Ehlers-Danlos syndrome (EDS) developed a symptomatic aneurysm of the superior mesenteric artery. His EDS diagnosis had been confirmed biochemically and genetically. Vascular complications are known to be associated with the vascular type of EDS, but this is the first report of a child with classical EDS who developed a major vascular complication. Clinicians should be aware that severe vascular complications albeit rare, can also occur in classical EDS.

Ehlers-Danlos arthrochalasia type (VIIA-B)--expanding the phenotype: from prenatal life through adulthood.

The Ehlers-Danlos syndromes (EDS) form a clinically and genetically heterogeneous group of inherited connective-tissue disorders characterized by joint hypermobility, tissue fragility and skin abnormalities. Six subtypes have been well characterized based on clinical features and molecular genetic abnormalities. The arthrochalasia type EDS (formerly types VIIA and B) is characterized by severe generalized joint hypermobility with multiple dislocations including congenital bilateral dislocation of the hips, muscular hypotonia and distinct dysmorphic features. The diagnosis of the arthrochalasia type EDS is of importance in the neonatal period because of consequences of physical disability in later life. However, the differential diagnosis may be difficult because of overlap with other hypermobility syndromes. In addition, the significant hypotonia may direct the physician toward various neuromuscular diagnoses. As patients become older, the hypotonia decreases and facial features become less distinct. In this report, we describe seven patients at different ages. Timing of diagnosis varied from prenatal life to adult age. The diagnosis of EDS type VII was confirmed by biochemical studies or mutation analysis showing characteristic mutations in COL1A1 and COL1A2. These mutations result in skipping of exon 6, which leads to defective collagen synthesis. For physicians treating patients with EDS type VII, achieving mobility for the patient is the greatest challenge and it may be impossible because of recurrent dislocations of nearly all joints in severe cases.

Vascular haemostasis.

SUMMARY: While the majority of this session will deal with selected inherited vascular abnormalities that may manifest as a haemorrhagic disorder, the initial discussion by Dr Key will focus on the interplay between the vessel wall and components of the coagulation system, with a focus on haemophilia A and B. Although it is generally accepted that physiological haemostasis is triggered by contact of blood with tissue factor (TF), there remains some controversy regarding the cellular origin of TF in vivo. In addition, the initiation and propagation of thrombin generation are highly dependent on the balance of pro- and anticoagulant functions of endothelium, a profile that varies significantly throughout the vasculature. Drs De Paepe and Malfait address heritable collagen disorders such as the Ehlers-Danlos syndromes (EDS), a heterogeneous group of diseases involving the skin, ligaments and joints, blood vessels and internal organs. Most EDS subtypes are caused by mutations in genes encoding fibrillar collagens, or in genes coding for enzymes involved in posttranslational modifications of collagens. Accurate biochemical and molecular testing is now available for most EDS subtypes and can direct genetic counselling and medical management for these disorders. Dr Shovlin reviews recent developments in hereditary haemorrhagic telengiectasia (HHT), a frequently undiagnosed disorder characterized by arteriovenous malformations in multiple organs. These abnormal blood vessels are the result of mutations in one of a number of genes whose protein products influence TGF-beta signalling in vascular endothelial cells. Several HHT management guidelines have been published and are discussed.

Recessive osteogenesis imperfecta caused by LEPRE1 mutations: clinical documentation and identification of the splice form responsible for prolyl 3-hydroxylation.

BACKGROUND: Recessive forms of osteogenesis imperfecta (OI) may be caused by mutations in LEPRE1, encoding prolyl 3-hydroxylase-1 (P3H1) or in CRTAP, encoding cartilage associated protein. These proteins constitute together with cyclophilin B (CyPB) the prolyl 3-hydroxylation complex that hydroxylates the Pro986 residue in both the type I and type II collagen alpha1-chains. METHODS: We screened LEPRE1, CRTAP and PPIB (encoding CyPB) in a European/Middle Eastern cohort of 20 lethal/severe OI patients without a type I collagen mutation. RESULTS: Four novel homozygous and compound heterozygous mutations were identified in LEPRE1 in four probands. Two probands survived the neonatal period, including one patient who is the eldest reported patient (17 7/12 years) so far with P3H1 deficiency. At birth, clinical and radiologic features were hardly distinguishable from those in patients with autosomal dominant (AD) severe/lethal OI. Follow-up data reveal that the longer lived patients develop a severe osteochondrodysplasia that overlaps with, but has some distinctive features from, AD OI. A new splice site mutation was identified in two of the four probands, affecting only one of three LEPRE1 mRNA splice forms, detected in this study. The affected splice form encodes a 736 amino acid (AA) protein with a "KDEL" endoplasmic reticulum retention signal. While western blotting and immunocytochemical analysis of fibroblast cultures revealed absence of this P3H1 protein, mass spectrometry and SDS-urea-PAGE data showed severe reduction of alpha1(I)Pro986 3-hydroxylation and overmodification of type I (pro)collagen chains in skin fibroblasts of the patients. CONCLUSION: These findings suggest that the 3-hydroxylation function of P3H1 is restricted to the 736AA splice form.

Total absence of the alpha2(I) chain of collagen type I causes a rare form of Ehlers-Danlos syndrome with hypermobility and propensity to cardiac valvular problems.

BACKGROUND: Heterozygous mutations in the COL1A1 or COL1A2 gene encoding the alpha1 and alpha2 chain of type I collagen generally cause either osteogenesis imperfecta or the arthrochalasis form of Ehlers-Danlos syndrome (EDS). Homozygous or compound heterozygous COL1A2 mutations resulting in complete deficiency of the proalpha2(I) collagen chains are extremely rare and have been reported in only a few patients, albeit with variable phenotypic outcome. METHODS: The clinical features of the proband, a 6 year old boy, were recorded. Analysis of proalpha and alpha-collagen chains was performed by SDS-polyacrylamide gel electrophoresis using the Laemmli buffer system. Single stranded conformation polymorphism analysis of the proband's DNA was also carried out. RESULTS: In this report we show that complete lack of proalpha2(I) collagen chains can present as a phenotype reminiscent of mild hypermobility EDS during childhood. CONCLUSIONS: Biochemical analysis of collagens extracted from skin fibroblasts is a powerful tool to detect the subset of patients with complete absence of proalpha2(I) collagen chains, and in these patients, careful cardiac follow up with ultrasonography is highly recommended because of the risk for cardiac valvular problems in adulthood.

Decreased expression of lysyl hydroxylase 2 (LH2) in skin fibroblasts from three Ehlers-Danlos patients does not result from mutations in either the coding or proximal promoter region of the LH2 gene.

The Ehlers-Danlos syndromes (EDS) are a heterogeneous group of inherited connective tissue disorders characterized by tissue fragility, hyperelasticity of the skin and joint hypermobility. This phenotype, accompanied by kyphoscoliosis and/or ocular fragility, is present in patients with the autosomal recessive type VI form of EDS. These patients have significantly decreased levels of lysyl hydroxylase (LH) activity, due to mutations in the LH1 gene. LH hydroxylates specific lysine residues in the collagen molecule that are precursors for the formation of cross-links which provide collagen with its tensile strength. No disorder has been directly linked to decreased expression of LH2 and LH3, two other isoforms of LH. This study describes 3 patients with mixed phenotypes of EDS, who have significantly decreased mRNAs for LH2, but normal levels of LH1 and LH3 mRNAs, in their skin fibroblasts. In contrast to the effect of LH1 deficiency in EDS VI patients, the decreased expression of LH2 does not affect LH activity, bifunctional collagen cross-links (measured after reduction as dihydroxylysinonorleucine (DHLNL) and hydroxylysinonorleucine (HLNL)), or helical lysine hydroxylation in these cell lines. Sequence analysis of full length LH2 cDNAs and 1kb of the promoter region of LH2 does not show mutations that could explain the decreased expression of LH2. These results suggest that the deficiency of LH2 in these fibroblasts may be caused by changes in other factors required for the expression of LH2.

Unusual oral findings in dermatosparaxis (Ehlers-Danlos syndrome type VIIC).

A 13-year-old patient with dermatosparaxis (Ehlers-Danlos syndrome type VIIC), an autosomal recessive disorder of procollagen-I-N-proteinase, is presented. The oral findings comprise micrognathia, hypodontia, localized microdontia, opalescent tooth discoloration, root dysplasia, pulp obliteration, severe gingival hyperplasia, frontal open bite, and severe restriction of TMJ mobility. The reported anomalies suggest the need for expanding the present phenotypic spectrum. This is the first report on oral findings in the syndrome.

The alphaE-catenin gene (CTNNA1) acts as an invasion-suppressor gene in human colon cancer cells.

The acquisition of invasiveness is a crucial step in the malignant progression of cancer. In cancers of the colon and of other organs the E-cadherin/catenin complex, which is implicated in homotypic cell-cell adhesion as well as in signal transduction, serves as a powerful inhibitor of invasion. We show here that one allele of the alphaE-catenin (CTNNA1) gene is mutated in the human colon cancer cell family HCT-8, which is identical to HCT-15, DLD-1 and HRT-18. Genetic instability, due to mutations in the HMSH6 (also called GTBP) mismatch repair gene, results in the spontaneous occurrence of invasive variants, all carrying either a mutation or exon skipping in the second alphaE-catenin allele. The alphaE-catenin gene is therefore, an invasion-suppressor gene in accordance with the two-hit model of Knudsen for tumour-suppressor genes.