Hereditary predisposition play an important role in thrombosis, especially in younger patients. Here we studied a young patient who experienced three different episodes of severe thromboses, some of which were life-threatening (pulmonary artery thrombosis, portal and mesenteric vein thrombosis, and arterial thrombosis of the lower leg). Blood levels of clotting related indicators were assessed. We screened 35 genes linked to thrombosis. We discovered a 756 kb duplication that spanned the F9 gene in region q27.1 of the X chromosome. The repeat includes the full F9 gene, thus, the patient had two functional copies of FIX with the FIX activity 192%. An identical repetition was found in the patient’s mother. Both the patient and his mother had high, but variable, plasma FIX activities that promote coagulation. The patient’s frequent, severe thrombolic events maybe attributed to the duplication of a big portion of the F9 gene and lupus anticoagulant positive.

中文翻译：

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伴有因子IX基因重复的复发性危及生命的血栓形成的研究

遗传倾向在血栓形成中起着重要作用，尤其是在年轻患者中。在这里，我们研究了一名年轻患者，他经历了三种不同的严重血栓形成，其中一些危及生命（肺动脉血栓形成、门静脉和肠系膜静脉血栓形成以及小腿动脉血栓形成）。评估凝血相关指标的血液水平。我们筛选了 35 个与血栓形成相关的基因。我们发现了一个 756 kb 的重复，跨越 X 染色体 q27.1 区域的 F9 基因。该重复包含完整的 F9 基因，因此，患者有两个 FIX 功能拷贝，FIX 活性为 192%。在患者的母亲身上也发现了相同的重复。患者和他的母亲都具有较高但可变的促进凝血的血浆 FIX 活性。该患者频繁、严重的血栓事件可能归因于大部分F9基因的重复和狼疮抗凝物阳性。