The MAC plays a critical role in the host defense mechanism by penetrating lipid bilayers, such as the outer membrane of gram-negative bacteria or the viral envelope.[11,12] A deficiency in C6 or any other protein component of the MAC predisposes the individual to recurrent neisserial infections, including meningococcal meningitis.[13] Among individuals with a complement deficiency, the incidence of meningococcal disease is 10,000-fold higher than that observed in the general population, and the recurrence rate is also reported to be higher (41% vs 0.34%).[3,14]. The gene discussed is C6; the disease is complement deficiency.