PurposeNearly 85%-90% of osteogenesis imperfecta (OI) cases are caused by autosome dominant mutations of COL1A1 and COL1A2 genes, of which de novo mutations cover a large proportion, whereas their characteristics remain to be elucidated. This study aims to compare the differences in clinical and genetic characteristics of de novo and inherited COL1A1/COL1A2 mutations of OI, assess the average paternal and maternal age at conception in de novo mutations, and research the rate of nonpenetrance in inherited mutations.Materials and MethodsA retrospective comparison between de novo and inherited mutations was performed among 135 OI probands with COL1A1/COL1A2 mutations. Mutational analyses of all probands and their family members were completed by Sanger sequencing. A new clinical scoring system was developed to assess the clinical severity of OI quantitatively.ResultsA total of 51 probands (37.78%) with de novo mutations and 84 probands (62.22%) with inherited mutations were grouped by the results of the parental gene verification. The proportion of clinical type III (P