MBL2 and hyperinsulinemic hypoglycemia, familial, 4: MBL deficiency (<1000 ng/ml) is mostly caused by a three-point mutation (O alleles) in exon 1 of the MBL gene (in codon 52, 54, 57) that disrupts the assembly of the oligomers and also by a promotor polymorphism (LX) that is associated with low MBL production.