Glycosaminoglycan alterations in osteogenesis imperfecta

Urinary GAGs from patients affected with Osteogenesis Imperfecta (O.I.) type I, type II and type III - according to Sillence et al. (1979) - have been investigated. Galactosamine to glucosamine ratio resulted significantly decreased in O.I. type II and III, whereas smaller differences in the mildest type of the disease were observed. Cellulose polyacetate electrophoresis of urinary GAGs purified from some patients showed the presence of a slowly moving polysaccharide substance, which did not appear in normal subjects. Moreover some pathological fractions, mainly constituted of ChS on the basis of chemical analysis and electrophoretic behaviour, were not digested by testicular hyaluronidase and presented anomalous structures as compared with the corresponding normal ones. These results seem to indicate that in some forms of O.I. the metabolic defect(s) not only affects the synthesis or the catabolism of a particular type of collagen, but also involves the proteoglycan component of the connective tissue.