The arthrochalasia type of Ehlers-Danlos syndrome (EDS Types VIIA or VIIB) is associated with defects in the amino-terminal ends in procollagen Type I chains that can result in weakening of collagen in connective tissues. Athrochalasia indicates severe and abnormal flaccidity of the joints. The diagnosis can be confirmed by laboratory testing.
Inheritance: autosomal dominant
Biochemical Defect: Deficient processing of the amino-terminal end of chains of collagen type I because of skipping of exon 6. In Type VIIA the pro-alpha1(I) chains are affected; in Type VIIB the pro-alpha2(I) chains are affected.
Major criteria:
(1) severe generalized joint hypermobility with recurrent subluxations
(2) congenital bilateral hip dislocations
Minor criteria:
(1) skin hyperextensibility
(2) tissue fragility with atrophic scars
(3) easy bruisability
(4) muscle hypotonia
(5) kyphoscoliosis
(6) mild osteopenia
Laboratory confirmation:
(1) electrophoresis of procollagen chains extracted from dermal fibroblasts
(2) demonstration of exon 6 skipping in cDNAs of COL1A1 or COL1A2
Distinction from EDS Type VI requires biochemical analysis.
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