osteogenesis imperfecta congenitaosteogenesis imperfecta tarda a group of connective tissue disorders of type I collagen, characterized by bone fragility, fractures on trivial trauma, skeletal deformity, blue sclerae, ligament laxity, and hearing loss. The Sillence system, which is a clinical, radiographic, and genetic classification, shows four types; inherited as autosomal dominant, caused by mutation in either the collagen type I alpha-1 gene (COL1A1) on chromosome 17q or the alpha-2 gene (COL1A2) on 7q. SYN: brittle bones.