Two possible reasons can be suggested for this difference: either our sample size was too small, due to autism being a highly heterogeneous complex disease, with many genes/loci and genetic variations involved, rather than being a distinct neurodevelopmental disorder [1, 31], or the methylation of ENO2 gene may have a “time course,” which could be in agreement with the DNA methylation process associated with brain development [6]. The gene discussed is ENO2; the disease is autism.