COL1A1/2 osteogenesis imperfecta (COL1A1/2-OI) is characterized by fractures with minimal or absent trauma, variable dentinogenesis imperfecta (DI), and, in adult years, hearing loss. The clinical features of COL1A1/2-OI represent a continuum ranging from perinatal lethality to individuals with severe skeletal deformities, mobility impairments, and very short stature to nearly asymptomatic individuals with a mild predisposition to fractures, normal dentition, normal stature, and normal life span. Fractures can occur in any bone but are most common in the extremities. DI is characterized by gray or brown teeth that may appear translucent, wear down, and break easily. COL1A1/2-OI has been classified into four types based on clinical presentation and radiographic findings. This classification system can be helpful in providing information about prognosis and management for a given individual. The four more common OI types are now referred to as follows: Classic non-deforming OI with blue sclerae (previously OI type I). Perinatally lethal OI (previously OI type II). Progressively deforming OI (previously OI type III). Common variable OI with normal sclerae (previously OI type IV).

COL1A1/2 osteogenesis imperfecta (COL1A1/2-OI) is characterized by fractures with minimal or absent trauma, variable dentinogenesis imperfecta (DI), and, in adult years, hearing loss. The clinical features of COL1A1/2-OI represent a continuum ranging from perinatal lethality to individuals with severe skeletal deformities, mobility impairments, and very short stature to nearly asymptomatic individuals with a mild predisposition to fractures, normal dentition, normal stature, and normal life span. Fractures can occur in any bone but are most common in the extremities. DI is characterized by gray or brown teeth that may appear translucent, wear down, and break easily. COL1A1/2-OI has been classified into four types based on clinical presentation and radiographic findings. This classification system can be helpful in providing information about prognosis and management for a given individual. The four more common OI types are now referred to as follows: Classic non-deforming OI with blue sclerae (previously OI type I). Perinatally lethal OI (previously OI type II). Progressively deforming OI (previously OI type III). Common variable OI with normal sclerae (previously OI type IV).

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized clinically by bone fragility and increased susceptibility to fractures. Osteogenesis imperfecta type IX (OI9) is a severe autosomal recessive form of the disorder (summary by van Dijk et al., 2009).

A rare multiple congenital malformations/dysmorphic syndrome characterized by osteogenesis imperfecta with multiple prenatal bone fractures, joint laxity, severe microcephaly, and bilateral cataracts. Additional reported manifestations include dysmorphic facial features (such as blue sclerae, hypertelorism, and low-set ears), lissencephaly, hydrocephalus, and cardiac and genital anomalies. The syndrome is lethal <i>in utero</i> or shortly after birth. There have been no further descriptions in the literature since 1978.

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized by bone fragility and low bone mass. Due to considerable phenotypic variability, Sillence et al. (1979) developed a classification of OI subtypes based on clinical features and disease severity: OI type I, with blue sclerae (166200); perinatal lethal OI type II, also known as congenital OI (166210); OI type III, a progressively deforming form with normal sclerae (259420); and OI type IV, with normal sclerae (166220). Most forms of OI are autosomal dominant with mutations in one of the 2 genes that code for type I collagen alpha chains, COL1A1 (120150) and COL1A2 (120160). Keupp et al. (2013) and Pyott et al. (2013) described osteogenesis imperfecta type XV, an autosomal recessive form of the disorder characterized by early-onset recurrent fractures, bone deformity, significant reduction of bone density, short stature, and, in some patients, blue sclera. Tooth development and hearing are normal. Learning and developmental delays and brain anomalies have been observed in some patients.