FMR1 and immunodeficiency disease: For example, fragile X syndrome derives from the silencing of the fragile X mental retardation 1 (FMR1) gene by a de novo methylation of a CGG region in its untranslated region, and immunodeficiency, centromeric region instability and facial anomalies (ICF1) syndrome is caused by alterations of the DNA methyl transferase 3b (DNMT3b) gene, an enzyme indispensable for methylation patterns [10,11].