Abstract
BackgroundComplement Factor I (CFI) is a serine protease with an important role in complement alternative pathway regulation. Complete factor I deficiency is strongly associated with severe infections. Approximately 30 families with this deficiency have been described worldwide.Patients and methodsWe have studied five new Spanish families suffering from CFI deficiency. From 19 screened people, 7 homozygous, 10 heterozygous and 2 healthy subjects were identified. Clinical, biochemical and genetic descriptions are included.ResultsMolecular studies demonstrated 4 novel mutations in the screened individuals; amongst them, we describe here the first great gene deletion reported in the CFI locus, which includes full exon 2 and part of the large intron 1.ConclusionCFI deficiency is possibly an underestimated defect and the eventual existence of this deficiency should be tested in those patients exhibiting low C3 and recurrent bacterial infections. We propose a simple diagnostic flowchart to help clinicians in the identification and correct diagnosis of such patients.
Highlights
Complement Factor I (CFI) is a serine protease with an important role in complement alternative pathway regulation
Molecular studies demonstrated 4 novel mutations in the screened individuals; amongst them, we describe here the first great gene deletion reported in the CFI locus, which includes full exon 2 and part of the large intron 1
III.4 and IV.4, brother and sister of III.1 and IV.1 respectively, were completely CFI deficient, they had no clinical signs related with this defect by the time the study was performed
Summary
Complement Factor I (CFI) is a serine protease with an important role in complement alternative pathway regulation. The human complement system consists of more than 35 plasma or membrane-bound proteins whose activation is tightly controlled through the action of complement inhibitors. Complement deficiencies, acquired or hereditary, affecting all the soluble components and many of the membrane-anchored receptors and regulators have been described in humans. Most of these deficiencies are inherited as autosomal recessive. The light chain (38KDa) contains the serine protease (SP) domain with the conserved catalytic residues [8] The gene of this complement regulator (CFI, OMIM*217030) comprises 13 exons localized on chromosome 4q25 [9,10] and its deficiency is inherited in an autosomal recessive manner
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