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Ehlers-Danlos syndrome, arthrochalasis type
Ehlers-Danlos syndromes (EDS) form a heterogeneous group of hereditary connective tissue diseases characterized by joint hyperlaxity, cutaneous hyperelasticity and tissue fragility. The incidence of the arthrochalasic form (formerly divided into types VIIA and VIIB) is very low. The disease is marked by bilateral congenital hip dislocation, hyperlaxity of the joints, and recurrent partial dislocations. Other signs include hyperextensible skin, fragile tissues with atrophic scars, and muscular hypotonia. Arthrochalasic EDS is transmitted as an autosomal dominant trait. It is due to abnormal maturation of the alpha1 (I) (former type VIIA) or alpha2 (I) (former type VIIB) collagen I pro-chains, in which the aminoterminal propeptide is incorrectly cleaved. The mutation causes skipping of exon 6 in the COL1A1 or COL1A2 gene and thus elimination of the cleavage site for N-terminal procollagen I peptidase. The clinical diagnosis is confirmed by the biochemical study of collagen I aminoterminal propeptides in cultured fibroblasts, or by molecular analysis revealing partial or total skipping of exon 6 in the COL1A1 or COL1A2 genes. Arthrochalasic EDS patients should be managed by specialist teams.
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