Systemic capillary leak syndrome (SCLS) is a rare condition associated with episodes of hypotension, hemoconcentration, hypoalbuminemia, and rhabdomyolysis. We describe a middle-aged man presenting with several distinct SCLS-like episodes, the last being fatal. In addition, in the year before the final event, he developed rapid cognitive decline with contrast-enhancing lesions on MRI and highly elevated neurofilament light protein levels in CSF.

Data and imaging were obtained from patient medical records.

At the time, the SCLS-like episodes were interpreted as myositis secondary to viral infection. A thorough workup for other causes, including genetic testing, was negative. As for the rapid cognitive decline, despite an extensive workup for infectious and inflammatory causes, no definitive diagnosis was made. Whole genome sequencing however identified a C9orf72 hexanucleotide expansion.

The C9orf72 expansion is associated with frontotemporal dementia and amyotrophic lateral sclerosis but has also been shown to increase susceptibility to neuroinflammation. Recent findings also suggest C9orf72 to exert functions in the immune system, in particular regulation of type I interferon responses, in turn shown to be associated with SCLS. This case suggests a possible link between SCLS, cerebral inflammation, dysregulated type I interferon signaling, and expansions in C9orf72.

全身性毛细血管渗漏综合征 (SCLS) 是一种与低血压、血液浓缩、低白蛋白血症和横纹肌溶解症发作相关的罕见病症。我们描述了一名中年男子出现数次明显的 SCLS 样发作，最后一次是致命的。此外，在最终事件的前一年，他的认知能力迅速下降，MRI 上出现对比增强病变，CSF 中神经丝轻蛋白水平显着升高。

数据和成像是从患者病历中获得的。

当时，SCLS 样发作被解释为继发于病毒感染的肌炎。对其他原因（包括基因检测）进行的彻底检查结果为阴性。至于认知能力的快速下降，尽管对感染和炎症原因进行了广泛的检查，但仍未做出明确的诊断。然而，全基因组测序鉴定出C9orf72六核苷酸扩增。

C9orf72扩增与额颞叶痴呆和肌萎缩性侧索硬化症有关，但也被证明会增加对神经炎症的易感性。最近的研究结果还表明C9orf72在免疫系统中发挥作用，特别是调节 I 型干扰素反应，这反过来又与 SCLS 相关。该病例表明 SCLS、脑炎症、I 型干扰素信号失调和C9orf72扩增之间可能存在联系。