Characterisation of Prader-Willi syndrome (PWS) genetic findings
| PWS 15q11-q13 deletion n=303 (60%) | PWS maternal disomy 15 n=185 (36%) | PWS imprinting defect n=22 (4%) | ||||||
| Deletion | n | Percentage | Maternal disomy 15 | n | Percentage | Imprinting defect | n | Percentage |
| Type I | 118 | 38.9 | Total isodisomy | 13 | 12.5 | Epimutation | 13 | 76.5 |
| Type II | 165 | 54.5 | Segmental isodisomy | 60 | 57.7 | Microdeletion | 4 | 23.5 |
| Atypical | 20 | 6.6 | Heterodisomy | 31 | 29.8 | Not established* | 5 | – |
| Not established† | 81 | – | ||||||
↵*Biparental (normal) inheritance was established using genotyping of chromosome 15 DNA markers. However, high-resolution SNP microarray analysis to determine the presence or absence of a microdeletion was not done due to lack of genetic material from the subject with PWS and/or parent(s) at the time of study. Percentage is based on the total number of 17 subjects with an imprinting defect.
↵†Maternal disomy 15 subclass was determined using high-resolution SNP microarray analysis and/or comprehensive genotyping of chromosome 15 DNA markers but not established due to lack of genetic material from the subject and/or parent(s) at the time of study. Percentage is based on the total number of 104 subjects with maternal disomy 15 subclass.