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Background: The Ehlers-Danlos syndromes (EDS) are heritable disorders of connective tissue (HDCT), reclassified in the 2017 nosology into 13 subtypes. The genetic basis for hypermobile Ehlers-Danlos syndrome (hEDS) remains unknown., Methods: Whole exome sequencing (WES) was undertaken on 174 EDS patients recruited from a national diagnostic service for complex EDS and a specialist clinic for hEDS. Patients had already undergone expert phenotyping, laboratory investigation and gene sequencing, but were without a genetic diagnosis. Filtered WES data were reviewed for genes underlying Mendelian disorders and loci reported in EDS linkage, transcriptome and genome-wide association studies (GWAS). A genetic burden analysis (Minor Allele Frequency (MAF) <0.05) incorporating 248 Avon Longitudinal Study of Parents and Children (ALSPAC) controls sequenced as part of the UK10K study was undertaken using TASER methodology., Results: Heterozygous pathogenic (P) or likely pathogenic (LP) variants were identified in known EDS and Loeys-Dietz (LDS) genes. Multiple variants of uncertain significance where segregation and functional analysis may enable reclassification were found in genes associated with EDS, LDS, heritable thoracic aortic disease (HTAD), Mendelian disorders with EDS symptomatology and syndromes with EDS-like features. Genetic burden analysis revealed a number of novel loci, although none reached the threshold for genome-wide significance. Variants with biological plausibility were found in genes and pathways not currently associated with EDS or HTAD., Conclusions: We demonstrate the clinical utility of large panel-based sequencing and WES for patients with complex EDS in distinguishing rare EDS subtypes, LDS and related syndromes. Although many of the P and LP variants reported in this cohort would be identified with current panel testing, they were not at the time of this study, highlighting the use of extended panels and WES as a clinical tool for complex EDS. Our results are consistent with the complex genetic architecture of EDS and suggest a number of novel hEDS and HTAD candidate genes and pathways., Competing Interests: Competing interests: TA is co-founder and director of the company BioCaptiva. There are no other competing interests., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Background: The Ehlers-Danlos syndromes (EDS) are a group of connective tissue disorders with several recognised types. Patients with a type of EDS have connective tissue abnormalities resulting in a varying degree of joint hypermobility, skin and vascular fragility and generalised tissue friability. Classical EDS (cEDS) typically occurs as a result of dominant pathogenic variants in COL5A1 or COL5A2 . The cardinal features of cEDS are hyperextensible skin, atrophic scarring and joint hypermobility. Arterial complications are more characteristically a feature of vascular EDS although individual cases of arterial events in cEDS have been reported., Methods: A cohort of 154 patients with a clinical diagnosis of cEDS from the UK was analysed., Results: Seven patients (4.5%) with a diagnosis of cEDS (four pathogenic, one likely pathogenic and two variants of uncertain significance in COL5A1 ) who had experienced arterial complications were identified. Arterial complications mostly involved medium-sized vessels and also two abdominal aortic aneurysms. No unique clinical features were identified in this group of patients., Conclusion: There is a possible increased risk of arterial complications in patients with cEDS, although not well-defined. Clinicians need to be aware of this possibility when presented with a patient with an arterial complication and features of cEDS. Long-term management in families with cEDS and a vascular complication should be individually tailored to the patient's history and their family's history of vascular events., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

A large family with dominantly inherited rhegmatogenous retinal detachment, premature arthropathy, and development of phalangeal epiphyseal dysplasia, resulting in brachydactyly was linked to COL2A1, the gene encoding proalpha1(II) collagen. Mutational analysis of the gene by exon sequencing identified a novel mutation in the C-propeptide region of the molecule. The glycine to aspartic acid change occurred in a region that is highly conserved in all fibrillar collagen molecules. The resulting phenotype does not fit easily into pre-existing subgroups of the type II collagenopathies, which includes spondyloepiphyseal dysplasia, and the Kniest, Strudwick, and Stickler dysplasias.

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders. Recently mutations have been found in the genes for type V collagen in a small number of people with the most common forms of EDS, types I and II. Here we characterise a COL5A2 mutation in an EDS II family. Cultured dermal fibroblasts obtained from an affected subject synthesised abnormal type V collagen. Haplotype analysis excluded COL5A1 but was concordant with COL5A2 as the disease locus. The entire open reading frame of the COL5A2 cDNA was directly sequenced and a single base mutation detected. It substituted a glycine residue within the triple helical domain (G934R) of alpha2(V) collagen, typical of the dominant negative changes in other collagens, which cause various other inherited connective tissue disorders. All three affected family members possessed the single base change, which was absent in 50 normal chromosomes.

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders characterised by skin hyperextensibility, joint hypermobility, easy bruising, and cutaneous fragility. Nine discrete clinical subtypes have been classified. We have investigated the molecular defect in a patient with clinical features of Ehlers-Danlos syndromes types I/II and VII. Electron microscopy of skin tissue indicated abnormal collagen fibrillogenesis with longitudinal sections showing a marked disruption of fibril packing giving very irregular outlines to transverse sections. Analysis of the collagens produced by cultured fibroblasts showed that the type V collagen had a population of alpha 1 (V) chains shorter than normal. Peptide mapping suggested a deletion within the triple helical domain. RTPCR amplification of mRNA covering the whole of this domain of COL5A1 showed a deletion of 54 bp. Although six Gly-X-Y triplets were lost, the essential triplet amino acid sequence and C-propeptide structure were maintained allowing mutant protein chains to be incorporated into triple helices. Genomic DNA analysis identified a de novo G+3-->T transversion in a 5' splice site of one COL5A1 allele. This mutation is analogous to mutations causing exon skipping in the major collagen genes, COL1A1, COL1A2, and COL3A1, identified in several cases of osteogenesis imperfecta and EDS type IV. These observations support the hypothesis that type V, although quantitatively a minor collagen, has a critical role in the formation of the fibrillar collagen matrix.

Generalised recessive dystrophic epidermolysis bullosa (EB) is a severe inherited disease in which patients suffer from blistering and scarring of the skin and mucous membranes after minor mechanical trauma. Tight genetic linkage has been established to the type VII collagen gene (COL7A1) at 3p21, with no evidence of locus heterogeneity. Several COL7A1 mutations have now been identified in recessive dystrophic EB patients. Prenatal diagnosis has been performed by examination of a fetal skin biopsy taken at about 16 weeks' gestation, and relies on identification of characteristic ultrastructural and immunohistochemical changes. We have now achieved a first trimester prenatal diagnosis using intragenic and flanking COL7A1 markers in a pregnancy at risk for recessive dystrophic EB. Segregation of the informative markers predicted the baby would be an unaffected carrier. The pregnancy continued to term and a healthy baby was born, confirming this result.

To strengthen the evidence for genetic linkage to COL7A1, we have studied 26 generalised recessive dystrophic epidermolysis bullosa (EB) families of British, Italian, Irish, and South African origin. We chose two linkage markers, a COL7A1 PvuII intragenic polymorphism and a highly informative anonymous microsatellite marker, D3S1100, which maps close to the COL7A1 locus at 3p21.1-3. Diagnosis was established by family history, clinical examination, immunofluorescence, and ultrastructural studies. The PvuII marker was informative in 16 families with a maximum lod score (Zmax) of 3.51 at recombination fraction (theta) = 0. The D3S1100 microsatellite was informative in 24 out of 25 families with Zmax = 6.8 at theta = 0.05 (Z = 4.94 at theta = 0) and no obligatory recombination events. These data strongly suggest that COL7A1 mutations cause EB in these families and, combined with previous studies, indicate locus homogeneity. The importance of anchoring fibrils for dermal-epidermal adhesion is further underlined. D3S1100 may later prove useful in prenatal diagnosis of this disease, if used in combination with other markers.

Previous studies have shown that Ehlers-Danlos syndrome type IV (EDS IV) is caused by mutations of type III collagen (COL3A1). Here we have characterised the most amino-terminal glycine substitution so far described in a patient with EDS IV. A combination of peptide mapping and chemical cleavage analysis of cDNA localised the mutation in cyanogen bromide peptide CB5. Sequence analysis showed a G to A mutation, converting glycine 661 to arginine, which was a new dominant mutation. Analysis of type III collagen secreted by cultured fibroblasts showed an overmodified mutant protein with normal thermal stability. However, the intracellularly retained form melted 2 degrees C lower than normal. This indicated that molecules resulting from the same mutation can differ in their thermal stabilities.

Ehlers-Danlos syndrome type IV is usually caused by mutations in COL3A1, the gene coding for type III collagen. In a woman with a milder form of this disease, analysis of type III collagen synthesised by her cultured skin fibroblasts showed an apparently shorter form of the protein. Amplification of overlapping cDNAs, encoding the triple helical region of the molecule, showed a deletion near the 5' end of the gene. Sequencing showed that exon 7 was missing from the cDNA sequence. Analysis of genomic DNA showed that this was the result of a T+6 to C+6 mutation in the donor splice site of intron 7. The proband's parents and 35 normal controls were homozygous for T+6 at this position, indicating that the C+6 mutation was causative.

Linkage of the anonymous marker D3S2 at 3p21 has been shown in three British families with dominant dystrophic epidermolysis bullosa with a combined lod score of 6.75 at theta = 0. This locus is close to the collagen type VII locus implying that abnormalities of this gene cause dominant dystrophic epidermolysis bullosa.

The clinical and biochemical observations in a patient with a mild form of Ehlers-Danlos syndrome (EDS) type IV are described. The patient's skin fibroblasts produced markedly diminished amounts of type III collagen. SDS-polyacrylamide gel electrophoresis of collagens produced by cells obtained from other, non-cutaneous tissues showed two forms of collagen alpha 1(III) chains, a normal and a slow migrating, mutant form. Further analysis confirmed that the type III collagen molecules containing mutant alpha chains which were overmodified had a lower thermal stability and were poorly secreted into the extracellular medium. The protein defect was mapped by in situ cyanogen bromide digestion and was located in alpha 1(III) CB9, the C-terminal peptide of the collagen triple helix. This study shows that non-cutaneous connective tissues can be a useful source for the study of type III collagen defects in patients with EDS type IV.

We have examined the type I collagen in a patient with type III/IV osteogenesis imperfecta. Two forms of alpha 1(I) chain were produced, one normal and the other containing a cysteine residue within the triple helical domain of the molecule. Cysteine is not normally present in this domain of type I collagen. Peptide mapping experiments localised the mutation to peptide alpha 1(I)CB3 which spans residues 403 to 551 of the triple helix. Subsequent PCR amplification of cDNA covering this region followed by sequencing showed a G to T single base change in the GGC codon for glycine 415 generating TGC, the codon for cysteine. The effect of the mutation on the protein is to delay secretion from the cell, reduce the thermal stability of the molecule by 2 degrees C, and cause excessive post-translational modification of all chains in molecules containing one or more mutant alpha 1(I) chains. The clinical phenotype observed in this patient and the position of the mutation conform to the recent prediction of Starman et al that Gly----Cys mutations in the alpha 1(I) chain have a gradient of severity decreasing from the C-terminus to the N-terminus.

We have studied a patient with Ehlers-Danlos syndrome type IV. Protein mapping studies of her type III collagen had indicated that cyanogen bromide fragment 9 contained the site of the mutation. Here we describe the mapping of this region for a single base mutation using a chemical modification and cleavage technique. Sequence analysis of cDNA showed a G to T mutation resulting in the substitution of glycine 910 by valine. This was confirmed by allele specific oligonucleotide hybridisation to the proband's genomic DNA.

The combined genetic data between the Marfan syndrome and 75 informative loci on 18 autosomes were used to construct an exclusion map for this disorder. Data are also presented for a further two unmapped markers. The most likely location of the Marfan syndrome gene is highlighted and all the unexcluded areas of the genome are displayed in a graphical form. This exclusion map shows that almost 75% of the genome has been excluded as a likely location for the Marfan syndrome gene in the majority of the families studied. Apart from chromosomes 8, 13, 21, and 22, for which no data were available, other regions not excluded yet include 5p, 6p, 9p, 10p, 12p, 15, 17p, 18, and 20p. Future linkage analysis using markers located in the highlighted regions should facilitate the identification of the site of the Marfan syndrome gene.

Six large families with classical Marfan syndrome were studied using markers on chromosomes 1 and 11. Two of three families tested showed negative scores using D1S7 but a third family gave a positive score (0.92) at theta = 0.1. The other chromosome 1 markers typed (MUCI, NGFB, D1S8) excluded close linkage. Negative lod scores with two chromosome 11q22 markers (D11S84, D11S148) excluded at least 20 cM in this area (Z = less than -2), which was chosen for study as two enzymes responsible for collagen degradation (collagenase and stromelysin) are localised to this region.

The detailed clinical features and progress of a child with homozygous alpha 2(I) collagen deficiency are described. Clinically, the disease presents as severe progressive Sillence type III osteogenesis imperfecta. The main biochemical defect is the synthesis of an abnormal pro alpha 2(I) chain which does not associate with pro alpha 1(I) chains and therefore is not incorporated into triple helical trimers of type I procollagen which can be used to assemble collagen fibres.

The Ehlers-Danlos type IV syndrome is a severe disease with premature death from catastrophic tearing of large arteries and a tendency to intestinal rupture. These patients lack the genetically distinct type III collagen. Here evidence is presented that obligate heterozygotes have lowered levels of type III collagen in their skin and that their cultured fibroblasts produce less than normal amounts of this protein. The inheritance is autosomal recessive.

Type I collagen is a heteropolymer of alpha 1(I) and alpha 2(I) chains, each of which is a separate product of genes localised to chromosomes 17 and 7 respectively. Molecular defects of type I collagen produce a group of inherited disorders of connective tissue primarily affecting bones, which are easily broken and collagen depleted (osteogenesis imperfecta). Sillence classifies these diseases into four groups, two of which are autosomal dominant and relatively mild, the others being either genetic lethals or responsible for very severe progressive disease. Here we describe two specific molecular abnormalities of type I collagen. One, a cysteine substitution in alpha 1(I) collagen, causes a mild Sillence type I disease, the other, a four base deletion in the C terminal extension of alpha 2(I) collagen, causes progressive Sillence type III disease in the homozygously affected patient and mild premature osteoporosis in his clinically symptomless parents. We have briefly reviewed a variety of other similar mutations causing various OI syndromes, which are tabulated, including various helical and non-helical deletions and a variety of structural protein changes. Several restriction fragment length polymorphisms for alpha 2(I) and alpha 1(II) collagens have also been described, and 5' EcoRI and 3' MspI polymorphisms for alpha 2(I) collagen segregate with Sillence type IV OI.