Chapter 5 99 Introduction Osteogenesis Imperfecta (OI), commonly defined as ‘brittle bones’ disease, is pathogenetically based on an hereditary collagen type I synthesis disorder, most often due to an autosomal dominant mutation in COL1A1 or COL1A2 genes. In addition to collagen type I genes, OI can be caused by multiple proteins connected to different parts of collagen biosynthesis 1. Therefore it includes broader characteristics like blue sclerae, hearing loss, dental problems, ligamentous laxity and short stature 2. The degree of impaired production of collagen type 1 is based on dominant pathogenic gene variants and results in a heterogeneous clinical expression historically classified in 5 types 3. The prevalence of OI is about 6-7 per 100,000 4. Easy bruising and bleeding are prominent features of some heritable connective tissue disorders such as Ehlers-Danlos, and is also commonly reported by OI patients 5–7. The literature for OI in relation with bleeding disorders is sparse and often dated 8–11. Bleeding disorders in heritable disorders of the connective tissue can be a result of fragility of capillaries and perivascular connective tissue, but can also be caused by a clotting problem due to platelet dysfunction, a defect in fibrinolysis or vascular components of the haemostasis 6. Although diagnosis of severe bleeding disorders such as moderate or severe hemophilia can be well defined, the distinction between individuals with or without a mild bleeding disorder is often difficult. The use of a bleeding assessment tool (BAT) in mild bleeding disorders can be more distinctive than a complete laboratory workup 12–14. Since clinical appreciation of presence and severity of bleeding symptoms is a fundamental step in the evaluation of a possible bleeding disorder in OI, the aim of this study is to describe the diverse aspects of bleeding and bruising in our whole cohort of OI patients using a structured questionnaire. We also intend to provide insight in the clinical consequences and give therapeutic considerations of bleeding in OI due to surgery, tooth extraction, menstruation and obstetrics. Methods A nationwide descriptive cohort study was undertaken in the Expert Center for adults with OI, Isala Hospital, Zwolle, the Netherlands. All known patients in our clinic with a clinical diagnosis of OI according to the OI classification of van Dijk and Sillence 3 were invited to fill in the self-bleeding assessment tool (Self-BAT) between October 2019 and August 2020. The Medical Ethics Committee of the Isala Hospital, Zwolle, The Netherlands, confirmed that the Medical Research Involving Human Subjects Act does not apply (reference number: 190513). All patients who were invited for this study signed an informed-consent form for study participation.
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