Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired haematopoietic stem cell disease which causes defects in complement inhibiting proteins. The disease presents classically with the triad of haemolytic anaemia, pancytopenia and thrombosis. Eculizumab, a humanized antibody that blocks the cleavage of complement factor 5, was approved for PNH treatment in 2007 and has improved patients' survival since then. However, several cases of invasive meningococcal disease (IMD) have been reported in eculizumab-treated patients, mostly caused by serogroup B infection which was not covered by the previously administered vaccine (MenACWY). We report a rare case of septic shock due to infection with Neisseria meningitis serogroup B despite prior vaccination with 4CMenB in a young PNH patient treated with eculizumab. There are increasing doubts over whether vaccination ensures sufficient immunoprotection against IMD in patients receiving eculizumab. Therefore, besides monitoring the immune response, lifelong chemoprophylaxis should be considered.
