CTNNB1 and hyperinsulinemic hypoglycemia, familial, 4: Examining associations between MMR gene deficiencies and the non-synonymous mutations described previously showed that within the BSA group, there was a negative association between MMR deficiency and CTNNB1 mutations as none of the eight CTNNB1-mutant patients was MMR-deficient versus 42% (8/19) of CTNNB1-wt tumours (p = 0.06).