Osteogenesis imperfecta (OI) is the result of a mutation in one of the two genes that carry instructions for making type 1 collagen (the major protein in bone and skin). Collagen is the major protein of the body’s connective tissue and can be likened to the framework around which a building is constructed. In OI, a person has either less collagen than normal, or a poorer quality of collagen than normal, leading to weak bones that fracture easily. OI is most often caused by a mutation (error) in one of two genes affecting the production of collagen. Collagen is the main structural protein in the human body – like the framework or scaffolding of a building. The body uses collagen in bones, muscles, tendons, skin and many other areas to provide structural support. The two most common mutations cause either not enough collagen to be produced, or poor quality collagen – both resulting in structural weakness. A genetic mutation causing OI may have been inherited from one or both parents (who may or may not display OI themselves) or it can be the result of a new, random mutation. Genetic testing can determine if a person has OI and which Type it is, though a preliminary diagnosis is often made on sight by a doctor who is very familiar with the condition. OI is not something you can ‘catch’ or spread to others. It is not the result of poor nutrition or a lack of calcium (one of many old wives tales!). OI occurs equally among the sexes and affects people on every continent across the globe.