Severe infantile Bordetella pertussis pneumonia in monozygotic twins with a congenital C3 deficiency

Bordetella pertussis or whooping cough is a vaccine-preventable disease that still remains a serious infection in neonates and young infants. We describe two young infants, monozygotic twins, with a severe B. pertussis pneumonia of whom one needed extracorporeal membrane oxygenation. Diagnostic work-up of unexplained hematuria and proteinuria during the illness revealed low serum complement component 3 (C3) levels. During follow-up, C3 levels remained low (400-600 mg/L). Extensive analysis of the persistent low C3 levels revealed an unknown heterozygous mutation in the C3 gene in both siblings and their mother. This C3 mutation in combination with the specific virulence mechanisms of B. pertussis probably contributed to the severe disease course in these cases. Conclusion: We propose that genetically caused complement disorders should be considered when confronted with severe cases of B. pertussis infection.