This effect is prevalent in skeletal conditions such as osteomalacia or ‘soft bones’, wherein the proportion of mineral to collagen is reduced (Berry et al., 2002), whereas in osteogenesis imperfecta (OI) or ‘brittle bone disease’, the deficient bone matrix is hypermineralised in patients carrying mutations in the genes encoding the type I procollagen chains (COL1A1 or COL1A2) (Boyde et al., 1999; Forlino et al., 2011). The gene discussed is COL1A2; the disease is osteogenesis imperfecta.