| Phenotype | Observed among selected 11 biallelic carriers | Age/course or interpretation |
|---|---:|---|
| Colorectal polyposis | 9/11 (82%) | Usually recognized in the third decade; dominant gastrointestinal manifestation in this clinically selected historical series. (pqac-00000002) |
| Acute myeloid leukemia or myelodysplastic syndrome | 7/11 (64%) | Mean age at diagnosis 35 years (range 30–49); typically early-adult-onset hematologic disease. (pqac-00000002) |
| Colorectal cancer | 2/11 (18%) | Reported less often than polyposis in the selected cases; age-specific cumulative risk is unknown. (pqac-00000002) |
| Schwannoma | 3/11 (27%) | Recurrent extracolonic tumor manifestation, but organ-specific risk and natural history remain undefined. (pqac-00000002) |
| Uveal melanoma | 2/11 (18%) | Part of the reported biallelic syndrome spectrum; monoallelic germline MBD4 loss with somatic loss of the wild-type allele represents a distinct uveal-melanoma-predisposition phenotype. (pqac-00000002) |
| Interpretation limitation | 11 clinically ascertained carriers from 8 families | These proportions are descriptive case frequencies, not population penetrance estimates; ascertainment, referral, relatedness, and very small sample size preclude reliable lifetime-risk calculations. (pqac-00000002) |


*Table: Phenotypes reported among the 11 historical biallelic MBD4 carriers summarized by Terradas et al. (2023). Frequencies describe a selected case series and must not be interpreted as population penetrance.*