OSTEOGENESIS IMPERFECTA - CLINICAL, CEPHALOMETRIC, AND BIOCHEMICAL INVESTIGATIONS OF OI TYPE-I, TYPE-III, AND TYPE-IV

The aim of the study was to analyze craniofacial development in 54 pat ients with osteogenesis imperfecta (OI), who were classified into OI t ypes I, III, and IV according to clinical criteria, and to relate the findings to the abnormalities in collagen I production. In 33 patients , analysis of radioactively labelled procollagen was performed. Cephal ometric radiographs, facial photographs, and CT-scans (a single case) were analyzed and mean facial diagrams for lateral and frontal films w ere produced based on registration of 221 reference points. Radiograph s of 102 male and 51 female Danish students served as control material . In OI type I, size of the skull and jaws was generally slightly redu ced, but morphology war within normal limits. In OI type IV and especi ally type III more severe abnormalities were found; the cranial base w as flattened, the maxilla posteriorly inclined, and nearly all size-me asurements were reduced. In OI type III the sagittal jaw relations wer e reduced and a mandibular overjet recorded. Three OI type I patients, whose fibroblasts produced structurally abnormal collagen I, had the stature and several features in the craniofacial region, which corresp onded to those recorded for the OI type TV group. Also, in three OI ty pe IV patients whose fibroblasts produced a reduced amount of normal c ollagen I, craniofacial morphology showed several features resembling type I patients. We conclude that structural abnormalities of collagen I generally give rise to more severe alterations of the craniofacial features than a quantitative defect of collagen I. OI type I patients are only slightly affected in their craniofacial region, while patient s with OI type IV and especially type III are moderately to severely a ffected. The combined cephalometric and biochemical findings suggest t hat future classification of patients with osteogenesis imperfecta sho uld be based on biochemical/molecular and radiological analyses in com bination with clinical criteria rather than on clinical features alone .