As such, the clinical classification of OI consists of 5 different types (1–5) [6] In approximately 90% of patients with OI, dominant mutations in the genes COL1A1 and COL1A2 encoding respectively the alpha1 and alpha2 chains of the protein collagen type I, are identified [6]. The gene discussed is COL1A2; the disease is osteogenesis imperfecta.