We evaluated the complement system in 29 children (mean age: 4.5 years) who survived fulminant meningococcal septic shock. No terminal complement deficiencies were found. One patient, who experienced the most dramatic disease course, had a decreased haemolytic activity in the haemolysis-in-gel test for the alternative pathway. The properdin concentration in serum of this patient was < 0.1 microgram/ml (n = 17.1-27.7 micrograms/ml). Coagulation studies revealed a heterozygeous type I protein C deficiency as well. He was the only patient with a Neisseria meningitidis group Y infection.
Conclusion: Fulminant meningococcal disease due to uncommon serogroups should lead to screening of the alternative pathway of complement activation.