Osteogenesis imperfecta (OI) is a rare heterozygous connective tissue disordercaused by mutations in genes that affect collagen components (in most cases mutations in COL1A1 и COL1A2 genes). The current classification system includes 15 types of OI, one of which (type II) is characterized by 100% intrauterine or perinatal mortality. The structure of mortality in other OI types is poorly understood because of the heterogeneity of clinical symptoms and the severity of connective tissue damage. W present a clinical case of type III osteogenesis imperfecta, complicated by generalized osteoporosis with multiple fractures of vertebrae and tubular bones and progressive kyphoscoliosis. Late-initiated treatment led to progression of the disease and led to cardiopulmonary insufficiency and death of the patient. Our clinical case highlights the importance of timely diagnosis, treatment and regular observation in patients with OI.