Rare splicing mutation in COL1A1 gene identified by whole exomes sequencing in a patient with osteogenesis imperfecta type I followed by prenatal diagnosis: A case report and review of the literature

Osteogenesis imperfecta (OI) is a rare disease characterized by increased bone fragility and predisposition to fractures, bone deformities and other major signs such as dentinogenesis imperfecta, blue sclera and deafness. Over 90% of OI cases are caused by mutations in the COL1A1 and COL1A2 genes and the inheritance is autosomal dominant. We present a case of a couple requesting genetic counseling, because the man was diagnosed with OI on a clinical and radiological basis and the woman was pregnant. Whole exomes sequencing (WES) was performed in order to identify the mutation (s), followed by prenatal diagnosis. WES identified a rare splicing mutation c.1155 + 1G > C in the COL1A1 gene recognized to be pathogenic and subsequently confirmed by next generation sequencing. The carrier state of the mutation was excluded for the fetus, so the pregnancy was further pursued and a healthy baby was born at term. WES is a new and effective technique for detecting pathogenic variants in monogenic diseases and it is preferable to use such a technique in diseases with genetic heterogeneity especially when time does not allow another time-consuming diagnostic technique such classical Sanger sequencing. WES offers possibility to expand the global spectrum of OI pathogenic variants enabling the diagnosis of the disease.