A case of familial meningococcal disease due to deficiency in mannose-binding lectin (MBL).

A case of familial meningococcal meningitis is described, which involved a 18-year old boy, his mother, and his grandfather, from who all three suffered from meningococcal disease at about similar age (17-19 y), albeit with one or two generations in between. By studying the genetic variants of MBL, we found out that all three family members described carried the B, D variant mbl genes instead of the homozygous mbl A, A trait. Serum MBL levels within the family varied from <0.15 microgs per ml (for the B, D variant) up to 7.0 microgs per ml with 1.67 microgs per ml as mean serum level of a control population (n = 216); in the normal population, also incidental cases with serum levels of up to 16 (!) microg-equivalents per ml were observed, which occurred predominantly in elderly people and which are most likely to be explained by the acute-phase reactant behavior of MBL protein.