Summary of the non-concordant clinical and molecular features between ICF1 and ICF2–4 patients
| . | ICF1 . | ICF2–4 . |
|---|---|---|
| Immunodeficiency | More pronounced and earlier diagnosis | Less extreme Ig class deficiencies |
| Intellectual disability | Lower prevalence | Higher prevalence |
| Gender bias | No significant bias noted | Majority male |
| Satellite DNA hypomethylation | Satellite II and III (common to all ICF) subtelomeric hypomethylation | Satellite II and III; α-satellite hypomethylation |
| Telomere biology | Elevated TERRA expression and telomere shortening | Not reported |
| Germline gene promoter methylation | Hypomethylation and upregulation of MAEL and SYCE1 | Not reported |
| Genome-wide DNA methylation | Hypomethylation of promoters of germline genes | Hypomethylation of CpG-poor heterochromatin |
| CSR | Unexplored | Low IgG and IgA |
| . | ICF1 . | ICF2–4 . |
|---|---|---|
| Immunodeficiency | More pronounced and earlier diagnosis | Less extreme Ig class deficiencies |
| Intellectual disability | Lower prevalence | Higher prevalence |
| Gender bias | No significant bias noted | Majority male |
| Satellite DNA hypomethylation | Satellite II and III (common to all ICF) subtelomeric hypomethylation | Satellite II and III; α-satellite hypomethylation |
| Telomere biology | Elevated TERRA expression and telomere shortening | Not reported |
| Germline gene promoter methylation | Hypomethylation and upregulation of MAEL and SYCE1 | Not reported |
| Genome-wide DNA methylation | Hypomethylation of promoters of germline genes | Hypomethylation of CpG-poor heterochromatin |
| CSR | Unexplored | Low IgG and IgA |
TERRA, telomeric repeat-containing RNA.