Podcast
Questions and Answers
Which complement component deficiency is most likely to decrease immune complex clearance?
Which complement component deficiency is most likely to decrease immune complex clearance?
In the case of the 15-year-old female with recurrent Neisseria meningitidis infections, which complement component deficiency is most likely?
In the case of the 15-year-old female with recurrent Neisseria meningitidis infections, which complement component deficiency is most likely?
Which complement component deficiency is associated with increased susceptibility to recurrent infections, similar to the case of the 15-year-old male with occipital headache, stiff neck, and vomiting?
Which complement component deficiency is associated with increased susceptibility to recurrent infections, similar to the case of the 15-year-old male with occipital headache, stiff neck, and vomiting?
In the context of abnormal CH50 and AH50 results, which complement component deficiency is most likely present in these patients?
In the context of abnormal CH50 and AH50 results, which complement component deficiency is most likely present in these patients?
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What is the function of the C1q subcomponent in the classical pathway of complement activation?
What is the function of the C1q subcomponent in the classical pathway of complement activation?
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What initiates the lectin pathway of complement activation?
What initiates the lectin pathway of complement activation?
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In the alternative pathway, what process continuously self-activates at a low level?
In the alternative pathway, what process continuously self-activates at a low level?
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Which component takes the place of the C1 proteases in the lectin pathway of complement activation?
Which component takes the place of the C1 proteases in the lectin pathway of complement activation?
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What is the inheritance pattern for C1q deficiency?
What is the inheritance pattern for C1q deficiency?
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Which condition is associated with C1q deficiency?
Which condition is associated with C1q deficiency?
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What is the result of C1q deficiency on the CH50 test?
What is the result of C1q deficiency on the CH50 test?
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Which complement pathway activation is defective in C1q deficiency?
Which complement pathway activation is defective in C1q deficiency?
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What is a common clinical manifestation of C1q deficiency?
What is a common clinical manifestation of C1q deficiency?
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Which complement protein is involved in C1q deficiency?
Which complement protein is involved in C1q deficiency?
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What type of mutations predispose to systemic lupus erythematosus (SLE) in C1q deficiency?
What type of mutations predispose to systemic lupus erythematosus (SLE) in C1q deficiency?
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What are the OMIM features associated with C1q deficiency?
What are the OMIM features associated with C1q deficiency?
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Which receptor is affected by C1q deficiency?
Which receptor is affected by C1q deficiency?
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What is the result of AP activation in C1q deficiency?
What is the result of AP activation in C1q deficiency?
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Which complement protein is associated with increased complement activation in C1q deficiency?
Which complement protein is associated with increased complement activation in C1q deficiency?
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Which complement pathway activation is defective in MBL2?
Which complement pathway activation is defective in MBL2?
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What forms the C3 convertase in the classical pathway of complement activation?
What forms the C3 convertase in the classical pathway of complement activation?
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Which component replaces the C1 proteases in the lectin pathway of complement activation?
Which component replaces the C1 proteases in the lectin pathway of complement activation?
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What initiates the alternative pathway of complement activation?
What initiates the alternative pathway of complement activation?
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What results from the binding of another C3b to the C3 convertase in the alternative pathway?
What results from the binding of another C3b to the C3 convertase in the alternative pathway?
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Which complement protein deficiency is associated with an increased risk of severe, recurrent pyogenic sinus and respiratory tract infections?
Which complement protein deficiency is associated with an increased risk of severe, recurrent pyogenic sinus and respiratory tract infections?
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What is the characteristic clinical manifestation of hereditary angioedema due to C1 esterase inhibitor deficiency?
What is the characteristic clinical manifestation of hereditary angioedema due to C1 esterase inhibitor deficiency?
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Which complement inhibitor is prevented from forming due to a defect in the PIGA gene in paroxysmal nocturnal hemoglobinuria?
Which complement inhibitor is prevented from forming due to a defect in the PIGA gene in paroxysmal nocturnal hemoglobinuria?
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Which complement component deficiency can cause complement-mediated intravascular hemolysis and atypical venous thrombosis?
Which complement component deficiency can cause complement-mediated intravascular hemolysis and atypical venous thrombosis?
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What is the result of C1Q deficiency on the CH50 test?
What is the result of C1Q deficiency on the CH50 test?
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Which complement component deficiency is associated with hyperpigmentation and skin fragility?
Which complement component deficiency is associated with hyperpigmentation and skin fragility?
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In C1S gain of function (GOF), what is the result of CH50 test?
In C1S gain of function (GOF), what is the result of CH50 test?
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Which disorder is associated with mannose-binding lectin (MBL) deficiency?
Which disorder is associated with mannose-binding lectin (MBL) deficiency?
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What clinical manifestation is common in patients with C1 inhibitor deficiency?
What clinical manifestation is common in patients with C1 inhibitor deficiency?
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Which complement component deficiency leads to excessive AP activation and decreased CD46 levels?
Which complement component deficiency leads to excessive AP activation and decreased CD46 levels?
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What are the OMIM features associated with C4A and C4B deficiency?
What are the OMIM features associated with C4A and C4B deficiency?
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Which receptor is affected by C1q deficiency?
Which receptor is affected by C1q deficiency?
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What initiates the lectin pathway of complement activation?
What initiates the lectin pathway of complement activation?
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What type of mutations predispose to systemic lupus erythematosus (SLE) in C1R deficiency?
What type of mutations predispose to systemic lupus erythematosus (SLE) in C1R deficiency?
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Study Notes
- The text is from "Immunology Scope Monograph" about Inherited Disorders of the Complement System published by UpToDate in 1992.
- The complement system has three major pathways for activation: classical, lectin, and alternative.
- In the classical pathway, immune complexes bind C1, which then cleaves C4 and C2 to form C4bC2b and C3 convertase, resulting in C3a and C5 convertase.
- In the lectin pathway, lectins bind to repetitive sugars on microbial surfaces, activating mannan-binding lectin-associated serine proteases (MASPs) instead of C1 proteases.
- The alternative pathway continuously self-activates at a low level (C3 tickover) and generates C3b, which engages alternative pathway components to form C3 convertase and C5 convertase.
- A deficiency in C3 is most likely to decrease immune complex clearance.
- A 15-year-old female presents to the ED with meningitis caused by Neisseria meningitidis, and her CH50 and AH50 results are abnormal.
- The complement component most likely to be deficient in this patient is Mannose-binding lectin (MBL) or Properdin.
- Early complement deficiencies, such as C1-C4, increase the risk of severe, recurrent pyogenic sinus and respiratory tract infections, and SLE.
- Terminal complement deficiencies, such as C5-C9, increase susceptibility to recurrent Neisseria bacteremia.
- Complement regulatory protein deficiencies, such as C1 esterase inhibitor deficiency, cause hereditary angioedema due to unregulated activation of kallikrein and bradykinin, and characterized by low C4 levels. Paroxysmal nocturnal hemoglobinuria is a defect in the PIGA gene that prevents the formation of glycosylphosphatidylinositol (GPI) anchors for complement inhibitors, such as decay-accelerating factor (CD55) and membrane inhibitor of reactive lysis (CD59), causing complement-mediated intravascular hemolysis and dark urine. It can also cause atypical venous thrombosis, such as Budd-Chiari syndrome, portal vein, cerebral, or dermal thrombosis.
- The text mentions various complement components, pathways, and disorders, including C1, C4, C8, CH50, AH50, MBL, MASP-1/MASP-2, properdin, SLE, aHUS, and PNH.
- Various genetic inheritance patterns are mentioned, including autosomal recessive, autosomal dominant, X-linked recessive, and linked deletions.
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Description
Test your knowledge of inherited disorders of the complement system with this quiz. Explore the genetic inheritance, protein deficiencies, associated diseases, and laboratory features related to complement deficiencies.
