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cDanlos syndrome (EDS VI [MIM 225400]) is characterized at birth by severe muscular hypotonia (requiring often invasive neuromuscular workup), kyphoscoliosis that is progressive, severe joint hypermobility and luxations, and marked skin hyperelasticity. In addition, there is fragility of the skin with abnormal scarring, osteopenia without a tendency to fractures, often a Marfanoid habitus and microcornea, and occasionally rupture of the arteries and the eye globe. The disorder is caused by a deficiency of the enzyme collagen lysyl hydroxylase (LH1; EC 1.14.11.4; procollagen-lysine,2-oxoglutarate 5-dioxygenase), which normally hydroxylates lysyl residues in-Xaa-Lys-Gly-sequences of the helical region of the collagen a chains to-Xaa-Hyl-Gly-. In bone and other tissue collagens, two Hyl residues, one in each of two amino telopeptides o