Genotypic and Phenotypic Characteristics of 29 Patients With Rare Types of Osteogenesis Imperfecta: Average 5 Years of Follow-Up.

Osteogenesis imperfecta (OI) is a rare genetic disorder characterized by bone fragility and abnormal connective tissue. Ninety percent of OI patients are caused by two mutations of COL1A1 and COL1A2, and more investigation was needed to better understand the rare types of OI. We followed up 29 patients with rare types of OI for an average of 5.4 years, and genotype, height, bone mineral density (BMD), blood biochemical indexes, misdiagnosis, and fracture were recorded. IFITM5 gene mutation was found in 18 patients (62.1%), which represents the most common pathogenic gene of rare types of OI in Chinese population. Thirteen cases had once been misdiagnosed, and the initial misdiagnosis rate was 44.8% (13/29). The higher misdiagnosis rate should be paid attention to by clinicians and healthcare providers, and we also give corresponding suggestions. Compared with the non-bisphosphonate treatment group, patients treated with bisphosphonates had higher lumbar spine BMD, fewer fractures, and lower levels of β-CTX and osteocalcin. However, there was no significant difference between OI type V patients and non-type V patients. Our study enriched the knowledge of genotype and phenotype characteristics of OI patients with rare types and bisphosphonate therapy.

成骨不全症（OI）是一种罕见的遗传性疾病，其特征为骨骼脆弱和结缔组织异常。90%的成骨不全症患者是由COL1A1和COL1A2的两种突变引起的，需要更多的研究来更好地了解罕见类型的成骨不全症。我们对29例罕见类型成骨不全症患者进行了平均5.4年的随访，记录了基因型、身高、骨密度（BMD）、血液生化指标、误诊情况和骨折情况。在18例患者（62.1%）中发现了IFITM5基因突变，这是中国人群中罕见类型成骨不全症最常见的致病基因。13例患者曾被误诊，初始误诊率为44.8%（13/29）。临床医生和医疗服务提供者应重视较高的误诊率，我们也给出了相应的建议。与未使用双膦酸盐治疗组相比，使用双膦酸盐治疗的患者腰椎骨密度更高，骨折更少，β - CTX和骨钙素水平更低。然而，V型成骨不全症患者和非V型患者之间没有显著差异。我们的研究丰富了对罕见类型成骨不全症患者基因型和表型特征以及双膦酸盐治疗的认识。