Biochemical investigations of different forms of osteogenesis imperfecta. Evaluation of 44 cases.

Forty-four patients with Osteogenesis Imperfecta (O.I.) were divided into groups on the basis of clinical and genetic criteria and the alterations in collagen and glycosaminoglycans (GAG) in the subjects of each group were examined. The largest group of patients as affected with a mild form of O.I. and showed an increased ratio of type III to type I collagen in skin and an increase of the ratio of hydroxylysine diglycoside to monoglycoside in skin collagen. The group of patients affected with a severe nonlethal form of O.I. appeared to be heterogeneous both from a clinical and from a biochemical point of view. A marked increase of the diglycoside to monoglycoside ratio was observed in skin and urine, whereas the ratio of type III to type I collagen in skin was within the normal range or significantly decreased. Some of these patients also showed alterations involving proteoglycans, e.g. in urinary GAGs a decreased galactosamine to glucosamine ratio could be demonstrated. Similar and more marked alterations involving both collagen and GAG metabolism were observed in five children affected with a lethal form of O.I.