1 FA 2023 - @USMLERxStep1 by medpox (1).pdf

IMMUNOLOGY ` IMMUNOLOGY—IMMUNE RESPONSES SEC TION II 105 Complement disorders Complement protein deficiencies Early complement deficiencies (C1–C4)  risk of severe, recurrent pyogenic sinus and respiratory tract infections. C3b used in clearance of antigen-antibody complexes Ž  risk of SLE (think...

IMMUNOLOGY ` IMMUNOLOGY—IMMUNE RESPONSES SEC TION II 105 Complement disorders Complement protein deficiencies Early complement deficiencies (C1–C4)  risk of severe, recurrent pyogenic sinus and respiratory tract infections. C3b used in clearance of antigen-antibody complexes Ž  risk of SLE (think SLEarly). Terminal complement deficiencies (C5–C9)  susceptibility to recurrent Neisseria bacteremia. Complement regulatory protein deficiencies C1 esterase inhibitor deficiency Causes hereditary angioedema due to unregulated activation of kallikrein Ž  bradykinin. Characterized by  C4 levels. ACE inhibitors are contraindicated (also  bradykinin). Paroxysmal nocturnal hemoglobinuria A defect in the PIGA gene prevents the formation of glycosylphosphatidylinositol (GPI) anchors for complement inhibitors, such as decay-accelerating factor (DAF/CD55) and membrane inhibitor of reactive lysis (MIRL/CD59). Causes complement-mediated intravascular hemolysis Ž  haptoglobin, dark urine A. Can cause atypical venous thrombosis (eg, Budd-Chiari syndrome; portal vein, cerebral, or dermal thrombosis). A