Bay Jakob Thaning, Katzenstein Terese Lea, Kofoed Kristian, Patel Dustin, Skjoedt Mikkel-Ole, Garred Peter, Schejbel Lone
Laboratory of Molecular Medicine, Department of Clinical Immunology, Section 7631, Rigshospitalet, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
Department of Infectious Diseases both at Rigshospitalet, University Hospital, Rigshospitalet, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
Clin Immunol. 2015 Oct;160(2):315-8. doi: 10.1016/j.clim.2015.05.004. Epub 2015 May 16.
Factor I is an important regulator of the complement system. Lack of Factor I causes uncontrolled activation of the complement system leading to consumption of C3. Complete deficiency of Factor I is a rare condition and only around 40 cases has been reported in the literature. The clinical presentation of Factor I deficiency varies and includes severe recurrent bacterial infections, glomerulonephritis and autoimmune diseases. The patient, a 28-years old woman with consanguineous parents, presented with recurrent leukocytoclastic vasculitis in the lower extremities with no associated systemic involvement, and without increased infection tendency. Initial testing showed low C3 concentration and a detailed complement evaluation absence of complement Factor I. Sequencing revealed a homozygous missense mutation in exon 2 of the CFI gene (SCV000221312). Even though the clinical symptoms of CFI mutations vary among patients sole association with leukocytoclastic vasculitis redefines the clinical spectrum of complete Factor I deficiency.
I因子是补体系统的重要调节因子。I因子缺乏会导致补体系统不受控制地激活，进而导致C3消耗。I因子完全缺乏是一种罕见病症，文献中仅报道了约40例。I因子缺乏的临床表现各异，包括严重的复发性细菌感染、肾小球肾炎和自身免疫性疾病。该患者为一名28岁女性，父母近亲结婚，表现为下肢复发性白细胞破碎性血管炎，无相关全身受累，且无感染倾向增加。初步检测显示C3浓度低，详细的补体评估显示缺乏补体I因子。测序显示CFI基因外显子2存在纯合错义突变（SCV000221312）。尽管CFI突变的临床症状在患者中各不相同，但仅与白细胞破碎性血管炎相关就重新定义了I因子完全缺乏的临床谱。
