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Pearls & Oy-sters: Homozygous Complement Factor I Deficiency Presenting as Fulminant Relapsing Complement-Mediated

Elle Levit1, Janice Leon2, Matthew R Lincoln2

  • 1From the Yale University School of Medicine (E.L.), New Haven, CT; Miami VA Healthcare System (J.L.), Veterans Health Administration, Miami, FL; Division of Neurology, Department of Medicine (M.R.L.), University of Toronto, ON; Keenan Research Centre for Biomedical Science (M.R.L.), Toronto, ON, Canada. elle.levit@uvmhealth.org.

Neurology
|March 20, 2023
PubMed

Insights

A rare genetic disorder affecting complement factor I (CFI) caused relapsing neurological symptoms. Treatment with IL-1β inhibition stabilized the patient, highlighting a potential therapeutic target.

Area of Science:

  • Immunology
  • Neurology
  • Genetics

Background:

  • The complement system, particularly the alternative pathway, plays a crucial role in innate immunity.
  • Complement factor I (CFI) is essential for regulating complement activation.
  • Deficiency in CFI can lead to uncontrolled complement activity and systemic inflammation.

Observation:

  • A 36-year-old male presented with recurrent neurological episodes including fever, headache, altered mental status, and focal deficits.
  • Neuroimaging showed reversible white matter lesions, and laboratory tests revealed low C3, low factor B, and absent alternative pathway activity.
  • A biopsy confirmed neutrophilic vasculitis.

Findings:

  • Genetic analysis identified a homozygous pathogenic variant in the complement factor I (CFI) gene.
  • This deficiency resulted in overactive alternative complement pathway, leading to consumption of C3 and factor B.
  • The patient's condition stabilized upon initiation of IL-1β inhibition therapy.

Implications:

  • Complement factor I deficiency is a rare but significant cause of relapsing neurological disease.
  • This case underscores the importance of considering complement disorders in patients with unexplained neurological and inflammatory symptoms.
  • Targeting IL-1β may represent a viable therapeutic strategy for complement-mediated neurological conditions.

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