What is the primary defect in Osteogenesis imperfecta?

The primary defect in Osteogenesis imperfecta is related to a collagen defect, specifically involving type I collagen, which is crucial for bone strength and structure. Osteogenesis imperfecta, often referred to as "brittle bone disease," results from genetic mutations that affect the synthesis and structure of collagen. This leads to bones that are fragile and susceptible to fractures with minimal or no trauma.

In this condition, the impaired collagen production does not provide adequate tensile strength to the bone matrix, resulting in deformities, frequent fractures, and other complications such as dental problems and hearing loss. The condition can also affect the skin and sclera due to the widespread role of collagen in connective tissue.

While other choices may relate to bone health—such as vitamin D deficiency, calcium metabolism disorders, and bone marrow failure—these are not the underlying factors driving the pathophysiology of Osteogenesis imperfecta. Instead, these conditions have distinct etiologies and do not directly cause the characteristic fragility seen in Osteogenesis imperfecta.