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<span>Complement factor I deficiency</span>
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<span class="page-url print-only">URL of this page: https://medlineplus.gov/genetics/condition/complement-factor-i-deficiency/</span>
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<h1>Complement factor I deficiency</h1>
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<div class="mp-exp exp-full" data-bookmark="description">
<h2>Description</h2>
<section><div class="mp-content"><p>Complement factor I deficiency is a disorder that affects the immune system. People with this condition are prone to recurrent infections, including infections of the upper respiratory tract, ears, skin, and urinary tract. They may also contract more serious infections such as pneumonia, meningitis, and <a class="image-modal" data-alt="The steps of sepsis. From the source of infection by bacteria, for example the lungs, the bacteria enter the blood steam, which leads to leaking blood vessels, dysfunction of multiple organs, including the heart, kidneys, liver, lungs, and brain, and ultimately death." data-caption="" data-credit="Designua/Shutterstock.com" data-filepath="images/PX0000TG_PRESENTATION.jpeg" data-imgtype="genetics" data-pix="PX0000TG" data-sourceurl="" data-title="Sepsis" href="https://medlineplus.gov/images/PX0000TG_PRESENTATION.jpeg" id="PX0000TG_1" title="Show image">sepsis<img alt="" aria-hidden="true" class="image-modal-icon" src="https://medlineplus.gov/css/img/icon_camera_small.png"/></a>, which may be life-threatening.</p><p>Some people with complement factor I deficiency have a kidney disorder called glomerulonephritis with isolated C3 deposits. Complement factor I deficiency can also be associated with autoimmune disorders such as <a data-pid="16181" href="https://medlineplus.gov/genetics/condition/rheumatoid-arthritis/">rheumatoid arthritis</a> or <a data-pid="16327" href="https://medlineplus.gov/genetics/condition/systemic-lupus-erythematosus/">systemic lupus erythematosus</a> (SLE). Autoimmune disorders occur when the immune system malfunctions and attacks the body's tissues and organs.</p></div>
</section>
</div>
<div class="mp-exp exp-full" data-bookmark="frequency">
<h2>Frequency</h2>
<section><div class="mp-content"><p>Complement factor I deficiency is a rare disorder; its exact prevalence is unknown. At least 38 cases have been reported in the medical literature.</p></div>
</section>
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<div class="mp-exp exp-full" data-bookmark="causes">
<h2>Causes</h2>
<section><div class="mp-content"><p>Complement factor I deficiency is caused by mutations in the <i><a data-pid="18547" href="https://medlineplus.gov/genetics/gene/cfi/">CFI</a></i> gene. This gene provides instructions for making a protein called complement factor I. This protein helps regulate a part of the body's immune response known as the <a class="image-modal" data-alt="Diagram showing complement responding to a pathogen by triggering formation of a membrane attack complex, resulting in destruction of the pathogen" data-caption="" data-credit="ellepigrafica/Shutterstock.com" data-filepath="images/PX0001DC_PRESENTATION.jpeg" data-imgtype="genetics" data-pix="PX0001DC" data-sourceurl="" data-title="Complement and membrane attack complex (MAC)" href="https://medlineplus.gov/images/PX0001DC_PRESENTATION.jpeg" id="PX0001DC_2" title="Show image">complement system<img alt="" aria-hidden="true" class="image-modal-icon" src="https://medlineplus.gov/css/img/icon_camera_small.png"/></a>. The complement system is a group of proteins that work together to destroy foreign invaders (such as bacteria and viruses), trigger <a class="image-modal" data-alt="Illustration of a leukocyte in a blood vessel, showing it attach to the inside of the vessel wall through rolling adhesion, then tight adhesion. The leukocyte squeezes through the blood vessel wall, which is called extravasation, to get into the tissue to the site of inflammation, bacteria, or injury." data-caption="" data-credit="ellepigrafica/Shutterstock.com" data-filepath="images/PX0000W8_PRESENTATION.jpeg" data-imgtype="genetics" data-pix="PX0000W8" data-sourceurl="" data-title="Migration of white blood cell to the site of injury or infection" href="https://medlineplus.gov/images/PX0000W8_PRESENTATION.jpeg" id="PX0000W8_3" title="Show image">inflammation<img alt="" aria-hidden="true" class="image-modal-icon" src="https://medlineplus.gov/css/img/icon_camera_small.png"/></a>, and remove debris from cells and tissues. This system must be carefully regulated so it targets only unwanted materials and does not attack the body's healthy cells. Complement factor I and several related proteins protect healthy cells by preventing activation of the complement system when it is not needed.</p><p>Mutations in the <i>CFI</i> gene that cause complement factor I deficiency result in abnormal, nonfunctional, or absent complement factor I. The lack (deficiency) of functional complement factor I protein allows uncontrolled activation of the complement system. The unregulated activity of the complement system decreases blood levels of another complement protein called C3, reducing the immune system's ability to fight infections. In addition, the immune system may malfunction and attack its own tissues, resulting in autoimmune disorders.</p></div>
</section>
<section>
<div class="related-genes mp-exp exp-full">
<h3>Learn more about the gene associated with Complement factor I deficiency</h3>
<ul class="relatedmp">
<li><a href="https://medlineplus.gov/genetics/gene/cfi/">CFI</a></li>
</ul>
</div>
</section>
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<div class="mp-exp exp-full" data-bookmark="inheritance">
<h2>Inheritance</h2>
<section><div class="mp- mp-content"><p>This condition is inherited in an <a class="image-modal" data-alt="Both parents carry one copy of a mutated gene. In the next generation, one child is affected with the condition, two children are carriers, and one is unaffected and not a carrier." data-caption="" data-credit="U.S. National Library of Medicine" data-filepath="images/PX0000A4_PRESENTATION.jpeg" data-imgtype="genetics" data-pix="PX0000A4" data-sourceurl="" data-title="Autosomal recessive inheritance" href="https://medlineplus.gov/images/PX0000A4_PRESENTATION.jpeg" id="PX0000A4_1" title="Show image">autosomal recessive pattern<img alt="" aria-hidden="true" class="image-modal-icon" src="https://medlineplus.gov/css/img/icon_camera_small.png"/></a>, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.</p></div>
</section>
</div>
<div class="mp-exp exp-full" data-bookmark="synonyms">
<h2>Other Names for This Condition</h2>
<section>
<ul class="bulletlist">
<li>C3 inactivator deficiency</li> <li>Complement component 3 inactivator deficiency</li> <li>Hereditary factor I deficiency disease</li>
</ul>
</section>
</div>
<div class="mp-exp exp-full" data-bookmark="resources">
<h2>Additional Information & Resources</h2>
<section>
<div class="mp-content">
<h2>Genetic Testing Information</h2>
<ul>
<li><a href="https://www.ncbi.nlm.nih.gov/gtr/conditions/C0019250/" target="TheNewWin">Genetic Testing Registry: Hereditary factor I deficiency disease</a> <span class="desc-text"><img alt="From the National Institutes of Health" title="From the National Institutes of Health" src="https://medlineplus.gov/images/nih.png" class="imgdesc" width="25" height="16"></span></li>
</ul>
</div>
</section>
<section>
<div class="mp-content">
<h2>Patient Support and Advocacy Resources</h2>
<ul>
<li><a href="https://rarediseases.org/" target="TheNewWin">National Organization for Rare Disorders (NORD)</a></li>
</ul>
</div>
</section>
<section>
<div class="mp-content">
<h2>Clinical Trials</h2>
<ul>
<li><a href="https://clinicaltrials.gov/search?cond=%22Complement factor I deficiency%22" target="TheNewWin">ClinicalTrials.gov</a> <span class="desc-text"><img alt="From the National Institutes of Health" title="From the National Institutes of Health" src="https://medlineplus.gov/images/nih.png" class="imgdesc" width="25" height="16"></span></li>
</ul>
</div>
</section>
<section>
<div class="mp-content">
<h2>Catalog of Genes and Diseases from OMIM</h2>
<ul>
<li><a href="https://omim.org/entry/610984" target="TheNewWin">COMPLEMENT FACTOR I DEFICIENCY; CFID</a></li>
</ul>
</div>
</section>
<section>
<div class="mp-content">
<h2>Scientific Articles on PubMed</h2>
<ul>
<li><a href="https://pubmed.ncbi.nlm.nih.gov/?term=%28complement+factor+i+deficiency%5BTIAB%5D%29+AND+english%5Bla%5D+AND+human%5Bmh%5D+AND+%22last+3600+days%22%5Bdp%5D" target="TheNewWin">PubMed</a> <span class="desc-text"><img alt="From the National Institutes of Health" title="From the National Institutes of Health" src="https://medlineplus.gov/images/nih.png" class="imgdesc" width="25" height="16"></span></li>
</ul>
</div>
</section>
</div>
<div class="mp-exp exp-full" data-bookmark="references">
<h2>References</h2>
<section>
<div class="mp-content">
<ul>
<li>Baracho GV, Nudelman V, Isaac L. Molecular characterization of homozygous
hereditary factor I deficiency. Clin Exp Immunol. 2003 Feb;131(2):280-6. doi:
10.1046/j.1365-2249.2003.02077.x. <a href="https://pubmed.ncbi.nlm.nih.gov/12562389" target="TheNewWin">Citation on PubMed</a> or <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1808620/" target="TheNewWin">Free article on PubMed Central</a></li>
<li>Grumach AS, Leitao MF, Arruk VG, Kirschfink M, Condino-Neto A. Recurrent
infections in partial complement factor I deficiency: evaluation of three
generations of a Brazilian family. Clin Exp Immunol. 2006 Feb;143(2):297-304.
doi: 10.1111/j.1365-2249.2005.02988.x. <a href="https://pubmed.ncbi.nlm.nih.gov/16412054" target="TheNewWin">Citation on PubMed</a> or <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1809586/" target="TheNewWin">Free article on PubMed Central</a></li>
<li>Nilsson SC, Trouw LA, Renault N, Miteva MA, Genel F, Zelazko M, Marquart H,
Muller K, Sjoholm AG, Truedsson L, Villoutreix BO, Blom AM. Genetic, molecular
and functional analyses of complement factor I deficiency. Eur J Immunol. 2009
Jan;39(1):310-23. doi: 10.1002/eji.200838702. <a href="https://pubmed.ncbi.nlm.nih.gov/19065647" target="TheNewWin">Citation on PubMed</a></li>
<li>Pettigrew HD, Teuber SS, Gershwin ME. Clinical significance of complement
deficiencies. Ann N Y Acad Sci. 2009 Sep;1173:108-23. doi:
10.1111/j.1749-6632.2009.04633.x. <a href="https://pubmed.ncbi.nlm.nih.gov/19758139" target="TheNewWin">Citation on PubMed</a></li>
<li>Ponce-Castro IM, Gonzalez-Rubio C, Delgado-Cervino EM, Abarrategui-Garrido C,
Fontan G, Sanchez-Corral P, Lopez-Trascasa M. Molecular characterization of
Complement Factor I deficiency in two Spanish families. Mol Immunol. 2008
May;45(10):2764-71. doi: 10.1016/j.molimm.2008.02.008. Epub 2008 Mar 28. <a href="https://pubmed.ncbi.nlm.nih.gov/18374984" target="TheNewWin">Citation on PubMed</a></li>
<li>Vyse TJ, Morley BJ, Bartok I, Theodoridis EL, Davies KA, Webster AD, Walport
MJ. The molecular basis of hereditary complement factor I deficiency. J Clin
Invest. 1996 Feb 15;97(4):925-33. doi: 10.1172/JCI118515. <a href="https://pubmed.ncbi.nlm.nih.gov/8613545" target="TheNewWin">Citation on PubMed</a> or <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC507137/" target="TheNewWin">Free article on PubMed Central</a></li>
<li>Vyse TJ, Spath PJ, Davies KA, Morley BJ, Philippe P, Athanassiou P, Giles CM,
Walport MJ. Hereditary complement factor I deficiency. QJM. 1994
Jul;87(7):385-401. <a href="https://pubmed.ncbi.nlm.nih.gov/7922290" target="TheNewWin">Citation on PubMed</a></li>
</ul>
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