In this current study, the proportion of COL1A1/2 pathogenic variants in Ukrainian OI patients comprised 63.83%, which appears to be lower than in Northern Europe [e.g. in Estonian and Swedish (87%) and Finnish (91%) populations] (Hartikka et al., 2004; Lindahl et al., 2015; Zhytnik et al., 2017). The gene discussed is COL1A1; the disease is osteogenesis imperfecta.