Ehlers-Danlos syndrome type IV: Phenotypic consequences of a splicing mutation in one COL3A1 allele

Abstract

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 A-transition at the splice donor site of intron 41. It resulted in the splicing out of the exon 41 encoded sequence from αl(III) mRNA and the deletion of 36 amino acids from glycine7" to lysine"10 of the triple helical domain of αl(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 by cultured fibroblasts. The child probably had a spontaneous new mutation in one COL3A1 allele as only normal sequences were obtained from the corresponding amplified region of the parent's leucocyte DNA.