Osteogenesis imperfecta is characterized by a defect in which type of collagen?

Osteogenesis imperfecta (OI), commonly known as "brittle bone disease," is primarily characterized by a defect in type I collagen. This type of collagen is critical for providing structural support and strength to bones, tendons, and other connective tissues. In OI, mutations in the genes responsible for producing type I collagen lead to insufficient production or abnormal structure of this collagen, resulting in fragile bones that are prone to fractures with minimal trauma.

The relationship between type I collagen and OI is well-established; individuals with the disorder often exhibit symptoms such as frequent fractures, blue sclera, and varying degrees of skeletal deformities. This underlines the importance of type I collagen in maintaining bone density and structural integrity. Other types of collagen mentioned, such as type II, III, and IV, are associated with different connective tissue disorders and structural roles, but they do not play a primary role in the pathophysiology of osteogenesis imperfecta.