Step 1

Immunology 3

A 2-year-old girl is brought to the emergency department by her mother due to fever for the past day and acute-onset seizures in the last hour. Past medical history is unremarkable, and immunizations are up to date. His temperature is 38.7°C (101.6°F), pulse is 125/min, respirations are 26/min, and blood pressure is 90/55 mm Hg. Physical examination shows mild tachycardia, tachypnea, and a non-blanchable purpuric rash on the trunk and lower extremities.

Deficiency in which of the following complement proteins increases the risk for recurrent infection with the suspected etiologic agent in this case?

  • A) C3a
  • B) C3b
  • C) C4a
  • D) C5a
  • E) C5b


Danielle Uayan


Dr. Ted O'Connell