Fransiska Malfait

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.

Clinical and genetic aspects of Ehlers-Danlos syndrome, classic type

Classic Ehlers-Danlos syndrome is a heritable connective tissue disorder characterized by skin hyperextensibility, fragile and soft skin, delayed wound healing with formation of atrophic scars, easy bruising, and generalized joint hypermobility. It comprises Ehlers-Danlos syndrome type I and Ehlers-Danlos syndrome type II, but it is now apparent that these form a continuum of clinical findings and differ only in phenotypic severity. It is currently estimated that approximately 50% of patients with a clinical diagnosis of classic Ehlers-Danlos syndrome harbor mutations in the COL5A1 and the COL5A2 gene, encoding the α1 and the α2-chain of type V collagen, respectively. However, because no prospective molecular studies of COL5A1 and COL5A2 have been performed in a clinically well-defined patient group, this number may underestimate the real proportion of patients with classic Ehlers-Danlos syndrome harboring a mutation in one of these genes. In the majority of patients with molecularly characterized classic Ehlers-Danlos syndrome, the disease is caused by a mutation leading to a nonfunctional COL5A1 allele and resulting in haploinsufficiency of type V collagen. A smaller proportion of patients harbor a structural mutation in COL5A1 or COL5A2, causing the production of a functionally defective type V collagen protein. Most mutations identified so far result in a reduced amount of type V collagen in the connective tissues available for collagen fibrillogenesis. Inter- and intrafamilial phenotypic variability is observed, but no genotype-phenotype correlations have been observed. No treatment for the underlying defect is presently available for Ehlers-Danlos syndrome. However, a series of preventive guidelines are applicable.

Bleeding and bruising in patients with Ehlers-Danlos syndrome and other collagen vascular disorders

Easy bruising and bleeding are not only characteristic manifestations of clotting and platelet disorders, they are also prominent features in some heritable collagen disorders, such as the Ehlers–Danlos syndromes (EDS). The EDS comprise a heterogeneous group of connective tissue diseases sharing clinical manifestations in skin, ligaments and joints, blood vessels and internal organs. Most EDS subtypes are caused by mutations in genes encoding the fibrillar collagens type I, III and V, or in genes coding for enzymes involved in the post‐translational modification of these collagens. Easy bruising is, to a variable degree, present in all subtypes of EDS, and is because of fragility of the capillaries and the perivascular connective tissues. Vascular fragility affecting medium‐sized and large arteries and veins is typically observed in the vascular subtype of EDS, caused by a molecular defect in collagen type III, an important constituent of blood vessel walls and hollow organs. Extensive bruising, spontaneous arterial rupture, leading to severe internal bleeding or premature death, and rupture of hollow organs, such as the intestine or the gravid uterus are predominant features of this subtype. Haematological studies including evaluation of clotting factors, platelet aggregation and bleeding time are usually normal in patients with EDS, except for the Hess test (Rumple–Leede test), which may be abnormal, indicating capillary fragility. In some forms of EDS confirmation of the clinical diagnosis and subtype is possible with biochemical and molecular studies.

Mutations in FKBP10 cause recessive osteogenesis imperfecta and bruck syndrome

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue characterized by bone fragility and alteration in synthesis and posttranslational modification of type I collagen. Autosomal dominant OI is caused by mutations in the genes (COL1A1 or COL1A2) encoding the chains of type I collagen. Bruck syndrome is a recessive disorder featuring congenital contractures in addition to bone fragility; Bruck syndrome type 2 is caused by mutations in PLOD2 encoding collagen lysyl hydroxylase, whereas Bruck syndrome type 1 has been mapped to chromosome 17, with evidence suggesting region 17p12, but the gene has remained elusive so far. Recently, the molecular spectrum of OI has been expanded with the description of the basis of a unique posttranslational modification of type I procollagen, that is, 3‐prolyl‐hydroxylation. Three proteins, cartilage‐associated protein (CRTAP), prolyl‐3‐hydroxylase‐1 (P3H1, encoded by the LEPRE1 gene), and the prolyl cis‐trans isomerase cyclophilin‐B (PPIB), form a complex that is required for fibrillar collagen 3‐prolyl‐hydroxylation, and mutations in each gene have been shown to cause recessive forms of OI. Since then, an additional putative collagen chaperone complex, composed of FKBP10 (also known as FKBP65) and SERPINH1 (also known as HSP47), also has been shown to be mutated in recessive OI. Here we describe five families with OI‐like bone fragility in association with congenital contractures who all had FKBP10 mutations. Therefore, we conclude that FKBP10 mutations are a cause of recessive osteogenesis imperfecta and Bruck syndrome, possibly Bruck syndrome Type 1 since the location on chromosome 17 has not been definitely localized.

Musculoskeletal complaints, physical activity and health-related quality of life among patients with the Ehlers–Danlos syndrome hypermobility type

Purpose. To investigate the musculoskeletal complaints, physical activity (PA) and health-related quality of life (HRQoL) in patients with the Ehlers–Danlos syndrome hypermobility type (EDS-HT). Methods. Thirty-two female EDS-HT patients as defined by the Villefranche criteria and 32 gender- and age-matched healthy control subjects participated in the study. Data about musculoskeletal complaints were collected from a specific form developed for the study. Daily PA and HRQoL were evaluated by the Baecke questionnaire and the RAND 36-Item Health Survey (distributed by RAND), respectively. Results. A significant presence of joint pain, joint dislocations, muscle cramps, tendinitis, fatigue and headache were revealed in the EDS-HT patient group. Joint pain was reported as the most frequent and most severe symptom. The habitual PA level was diminished in the patient group. Specifically, EDS-HT subjects had significantly lower sport participation, but a comparable leisure time excluding sports compared to the healthy control subjects. All eight HRQoL dimensions of the RAND-36 and both physical and emotional summary scores were significantly impaired in EDS-HT. Conclusions. EDS-HT is characterised by various severe musculoskeletal complaints and has a detrimental effect on the habitual level of PA and HRQoL, in both physical and psychosocial dimension. An appropriate treatment and management in healthcare is needed.

The 2017 international classification of the Ehlers-Danlos syndromes.

The Ehlers–Danlos syndromes (EDS) are a clinically and genetically heterogeneous group of heritable connective tissue disorders (HCTDs) characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. Over the past two decades, the Villefranche Nosology, which delineated six subtypes, has been widely used as the standard for clinical diagnosis of EDS. For most of these subtypes, mutations had been identified in collagen‐encoding genes, or in genes encoding collagen‐modifying enzymes. Since its publication in 1998, a whole spectrum of novel EDS subtypes has been described, and mutations have been identified in an array of novel genes. The International EDS Consortium proposes a revised EDS classification, which recognizes 13 subtypes. For each of the subtypes, we propose a set of clinical criteria that are suggestive for the diagnosis. However, in view of the vast genetic heterogeneity and phenotypic variability of the EDS subtypes, and the clinical overlap between EDS subtypes, but also with other HCTDs, the definite diagnosis of all EDS subtypes, except for the hypermobile type, relies on molecular confirmation with identification of (a) causative genetic variant(s). We also revised the clinical criteria for hypermobile EDS in order to allow for a better distinction from other joint hypermobility disorders. To satisfy research needs, we also propose a pathogenetic scheme, that regroups EDS subtypes for which the causative proteins function within the same pathway. We hope that the revised International EDS Classification will serve as a new standard for the diagnosis of EDS and will provide a framework for future research purposes.

EMQN best practice guidelines for the laboratory diagnosis of osteogenesis imperfecta.

Osteogenesis imperfecta (OI) comprises a group of inherited disorders characterized by bone fragility and increased susceptibility to fractures. Historically, the laboratory confirmation of the diagnosis OI rested on cultured dermal fibroblasts to identify decreased or abnormal production of abnormal type I (pro)collagen molecules, measured by gel electrophoresis. With the discovery of COL1A1 and COL1A2 gene variants as a cause of OI, sequence analysis of these genes was added to the diagnostic process. Nowadays, OI is known to be genetically heterogeneous. About 90% of individuals with OI are heterozygous for causative variants in the COL1A1 and COL1A2 genes. The majority of remaining affected individuals have recessively inherited forms of OI with the causative variants in the more recently discovered genes CRTAP, FKBP10, LEPRE1,PLOD2, PPIB, SERPINF1, SERPINH1 and SP7, or in other yet undiscovered genes. These advances in the molecular genetic diagnosis of OI prompted us to develop new guidelines for molecular testing and reporting of results in which we take into account that testing is also used to ‘exclude’ OI when there is suspicion of non-accidental injury. Diagnostic flow, methods and reporting scenarios were discussed during an international workshop with 17 clinicians and scientists from 11 countries and converged in these best practice guidelines for the laboratory diagnosis of OI.

Total absence of the α2(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 α1 and α2 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 proα2(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 proα and α-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 proα2(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 proα2(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.

Comprehensive molecular analysis demonstrates type V collagen mutations in over 90% of patients with classic EDS and allows to refine diagnostic criteria

Type V collagen mutations are associated with classic Ehlers–Danlos Syndrome (EDS), but it is unknown for which proportion they account and to what extent other genes are involved. We analyzed COL5A1 and COL5A2 in 126 patients with a diagnosis or suspicion of classic EDS. In 93 patients, a type V collagen defect was found, of which 73 were COL5A1 mutations, 13 were COL5A2 mutations and seven were COL5A1 null‐alleles with mutation unknown. The majority of the 73 COL5A1 mutations generated a COL5A1 null‐allele, whereas one‐third were structural mutations, scattered throughout COL5A1. All COL5A2 mutations were structural mutations. Reduced availability of type V collagen appeared to be the major disease‐causing mechanism, besides other intra‐ and extracellular contributing factors. All type V collagen defects were identified within a group of 102 patients fulfilling all major clinical Villefranche criteria, that is, skin hyperextensibility, dystrophic scarring and joint hypermobility. No COL5A1/COL5A2 mutation was detected in 24 patients who displayed skin and joint hyperextensibility but lacked dystrophic scarring. Overall, over 90% of patients fulfilling all major Villefranche criteria for classic EDS were shown to harbor a type V collagen defect, which indicates that this is the major—if not only—cause of classic EDS. Hum Mutat 33:1485–1493, 2012.

Musculocontractural Ehlers-Danlos Syndrome (former EDS type VIB) and adducted thumb clubfoot syndrome (ATCS) represent a single clinical entity caused by mutations in the dermatan-4-sulfotransferase 1 encoding CHST14 gene.

We present clinical and molecular findings of three patients with an EDS VIB phenotype from two consanguineous families. The clinical findings of EDS kyphoscoliotic type (EDS type VIA and B) comprise kyphoscoliosis, muscular hypotonia, hyperextensible, thin and bruisable skin, atrophic scarring, joint hypermobility and variable ocular involvement. Distinct craniofacial abnormalities, joint contractures, wrinkled palms, and normal urinary pyridinoline ratios distinguish EDS VIB from EDS VIA. A genome‐wide SNP scan and sequence analyses identified a homozygous frameshift mutation (NM_130468.2:c.145delG, NP_569735.1:p.Val49*) in CHST14, encoding dermatan‐4‐sulfotransferase 1 (D4ST‐1), in two Turkish siblings. Subsequent sequence analysis of CHST14 identified a homozygous 20‐bp duplication (NM_130468.2:c.981_1000dup, NP_569735.1:p.Glu334Glyfs*107) in an Indian patient. Loss‐of‐function mutations in CHST14 were recently reported in adducted thumb–clubfoot syndrome (ATCS). Patients with ATCS present similar craniofacial and musculoskeletal features as the EDS VIB patients reported here, but lack the severe skin manifestations. By identifying an identical mutation in patients with EDS VIB and ATCS, we show that both conditions form a phenotypic continuum. Our findings confirm that the EDS‐variant associated with CHST14 mutations forms a clinical spectrum, which we propose to coin as “musculocontractural EDS” and which results from a defect in dermatan sulfate biosynthesis, perturbing collagen assembly.