Background Complement (C) factor I deficiency is a rare immunodeficiency state frequently
associated with recurrent pyogenic infections in early infancy. This deficiency causes a
permanent uncontrolled activation of the alternative pathway resulting in massive
consumption of C3. Patient A 23-year-old woman with monthly recurrent meningitis
episodes, mostly in the perimenstrual period, since August 1999. Previously, at age 16
years, she had meningococcal sepsis, also coinciding with menstruation. Objectives To …