A 24-year-old, previously healthy woman is evaluated for skin rash, joint pains, and renal failure. She is found to have decreased C3 and C4 levels and a normal factor B level. Which of the following most likely triggered the complement system activation in this patient?

Question

A 24-year-old, previously healthy woman is evaluated for skin rash, joint pains, and renal failure.  She is found to have decreased C3 and C4 levels and a normal factor B level.  Which of the following most likely triggered the complement system activation in this patient?

Quizplus · Accepted Answer

Eductional Objective: The binding of autoantibodies to host antigens can trigger the classical complement cascade, leading to low C4 and C3 levels.  Because autoantibodies do not activate the alternative complement cascade, factor B levels remain normal.  This pattern is frequently seen in rheumatologic diseases such as systemic lupus erythematosus.

A 24-Year-Old, Previously Healthy Woman Is Evaluated for Skin Rash