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.
Keywords: CFI; Complement Factor I; Complement deficiency; Complement regulation; Leukocytoclastic vasculitis.
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