A family with partial and total deficiency of complement C3

Area of Science:

• Immunology
• Genetics
• Infectious Disease

Background:

• Complement system proteins like C3 and C1q are crucial for innate and adaptive immunity.
• Deficiencies in complement components can lead to increased susceptibility to infections, particularly encapsulated bacteria.

Observation:

• A young girl presented with a complete absence of complement C3 and C1q.
• She experienced recurrent severe infections, including pneumococcal meningitis and pneumonia.
• Family studies revealed partial C3 deficiency in parents and some siblings, indicating a potential hereditary pattern.

Findings:

• The patient exhibited decreased immunoglobulin G (IgG) and elevated immunoglobulin M (IgM) levels.
• Post-mortem examination showed abnormal germinal center morphology in lymphoid tissues.
• These immunological and histological findings correlate with the observed clinical phenotype.

Implications:

• Complete C3 and C1q deficiency represents a severe form of primary immunodeficiency.
• Understanding these complement deficiencies aids in diagnosing and managing recurrent infections.
• This case highlights the critical role of the complement system in host defense against bacterial pathogens.