As before, DHFR-DD genotype was underrepresented among children with very-early onset (DD = 4.8%), and when compared with the rest of patients (DD = 15.7%) or with the late-onset subgroup (DD = 16.3%), the differences were statistically significant (P = 0.03 and P = 0.04, respectively), and this was also confirmed when DHFR-WD and -DD genotypes were combined (P = 0.03). Here, DHFR is linked to Wilson disease.