Ehlers-Danlos syndrome encompasses a group of inherited disorders of connective tissue, some of which are characterised by abnormalities of collagen metabolism. The chromosomal location, identified genes and biochemical defects, inheritance pattern, and clinical features for the various known subtypes are outlined. Prenatal diagnosis is possible for types IV, VI, VIIA1, and VIIA2. An unusual presentation of type IV Ehlers-Danlos syndrome in a 16 year old boy with an anterior myocardial infarction resulting from dissection of the left anterior descending coronary artery is reported here. A clinical diagnosis of type IV Ehlers-Danlos syndrome was made subsequently and confirmed by the reduced production, impaired secretion, and abnormally slow electrophoretic migration of type III collagen, indicating an underlying mutation in the COL3A1 gene. This patient represents the first case of type IV Ehlers-Danlos syndrome with symptomatic coronary artery dissection.
The features of a 32 year old woman with Ehlers-Danlos syndrome type VIIB and affected members of her family, resulting from a mutation in one COL1A2 allele, were studied. Her dermal type I collagen contained a2(I) chains and mutant pN-a2(I) chains in which the amino-terminal propeptide remained attached to the a2(I) chain. She was heterozygous for an AG-AC mutation at the splice acceptor site of intron 5 of the COL1A2 gene. The mutation activated a cryptic AG splice acceptor site corresponding to positions + 14 and + 15 of exon 6 of the COL1A2 gene. In contrast to previous reports only five, rather than all 18, amino acids encoded by exon 6 were deleted in the proband. The deleted peptide removed the amino-proteinase cleavage site, but not the nearby lysine cross linking site in the amino-telopeptide of the a2(I) chain.She was born with bilateral hip dislocations, knee subluxations, and generalised joint hypermobility. Bilateral inguinal herniae and an umbilical hernia were present at birth. Facial features included a depressed nasal bridge with prominent paranasal folds. The skin was soft, moderately hyperelastic, and sagged over the face. Skin fragility and easy bruising were apparent from childhood. Skin wounds healed slowly and with broad, paper thin scars. Throughout her life, she had multiple fractures of the small bones of her hands and feet following moderate trauma.
The features of a child with Ehlers-Danlos syndrome type IV (EDS IV) resulting from a mutation in one COL3A1 allele were studied. The child was heterozygous for a G-to Atransition at the splice donor site of intron 41. It resulted in the splicing out of the exon 41 encoded sequence from al(III) mRNA and the deletion of 36 amino acids from glycine7" to lysine"l0 of the triple helical domain of al(III) chains of type III collagen. The amount of type III collagen in the dermis was only about 11% of normal. The child had the acrogeric form of EDS IV. He had the characteristic facies with a pinched nose, thin lips, and prominent eyes. These facial features, his aesthenic build, thin skin, prominent subcutaneous veins, and aged hands produced a 'cachectic' appearance. These features were evident in early childhood and worsened up to 12j years when he was last reviewed. Spontaneous bruising, bleeding from the large bowel, constipation, and delayed gastric emptying were other features. In cross section, the dermal collagen fibrils were round and measured 93-3±11-5nm in diameter which was not significantly different from control values of 102-5 ± 13-4 nm. The serum type III procollagen amino-terminal propeptide level of 25-5 ng/ml was within the normal age matched values of 15-5 ± 7-7 ng/ml despite the low production of type III collagen
A novel heterozygous mutation of the COL3A1 gene that encodes the alpha 1(III) chains of type III collagen was identified in a family with the acrogeric form of Ehlers-Danlos syndrome type IV (EDS-IV). Cultured dermal fibroblasts produced normal and shortened alpha 1(III) chains. The triple helix of the latter chain was shortened owing to a 33 amino acid deletion of Gly-184 to Pro-216. The corresponding region of cDNA lacked 99 base pairs from nucleotides 1051 to 1149. The deletions corresponded exactly to the normal sequence encoded by exon 17 of the COL3A1 gene. The proband was heterozygous for a T to G transversion at position +2 of intron 17, which resulted in skipping of exon 17. The splicing defect was not corrected by growing the fibroblasts at 33 degrees C and no other splicing variants were identified at 33 or 37 degrees C. The affected brother had the same mutation but his unaffected mother did not. Heterotrimeric type III collagen molecules containing normal and mutant chains were retained within the cell. The mutant homotrimeric molecules were modified and secreted normally and were thermally stable. These normal characteristics of the mutant homotrimers suggested that the loss of ten Gly-Xaa-Yaa triplets (where Gly-Xaa-Yaa is a repetitive amino acid triplet structure in which Xaa and Yaa are other amino acids, proline and hydroxyproline being more common in the Yaa position) did not adversely affect the formation and stability of the triple helix or the structural requirements for secretion. However, the mutant homotrimers were not incorporated into the extracellular matrix of an in vitro model of EDS-IV dermis. The EDS-IV phenotype in this family was probably due to a deficiency in the amount of normal type III collagen available for formation of the heterotypic collagen fibrils of the extracellular matrix. Intracellular and extracellular quality-control mechanisms prevented the incorporation of heterotrimeric and homotrimeric mutant type III collagen molecules into the cross-linked extracellular matrix.
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