Based on the causative genes identified to date, ICF syndrome is currently categorized into five subtypes: ICF1 (OMIM#242860), ICF2 (OMIM#614069), ICF3 (OMIM#616910), ICF4 (OMIM#616911), and ICFX (OMIM# is unavailable). The gene discussed is DNMT3B; the disease is ICF syndrome.