A study of patients with suspected immunodeficiency found a higher number of homozygous and compound heterozygous patients with abnormal mannan-binding protein (MBP) alleles (variants B, C, and D). In the case group of 101 patients, one patient was homozygous for D and five were compound heterozygous for B/D. No patients in the control population of 47 patients were homozygous or compound heterozygous.
A study of the frequency of MBL2 variants was made comparing children meningococcal disease with controls. Of 266 patients, none were homozygous for R52C and 12 were compound heterozygous for R52C and either G54D or G57E. Of 382 controls, 3 were compound heterozygous for R52C.