Table 1.
Clinical Features of Individuals with Prader–Willi Syndrome (PWS)
| Clinical Features | Overall % |
|---|---|
| Gestation | |
| Reduced fetal activity | 76 |
| Nonterm delivery | 41 |
| Breech presentation | 26 |
| Early infancy | |
| Developmental delay | 98 |
| Hypotonia (weak muscle tone) | 94 |
| Feeding problems | 93 |
| Low birthweight | 30 |
| Brain function and behavior | |
| Mental deficiency | 97 |
| Personality problems | 41 |
| Seizures | 20 |
| Growth | |
| Obesity | 94 |
| Short stature | 76 |
| Delayed bone age | 50 |
| Face | |
| Narrow forehead | 75 |
| Almond-shaped eyes | 75 |
| Strabismus | 52 |
| Early dental cavities /enamel hypoplasia | 40 |
| Sexual development | |
| Hypogenitalism/hypogonadism (underdeveloped sex organs) | 95 |
| Cryptorchidism (undescended testicles) | 88 |
| Menstruation | 39 |
| Skeletal | |
| Small hands and feet | 83 |
| Scoliosis | 44 |
| Other | |
| Skin picking | 79 |
| Reduced glucose tolerance/diabetes mellitus | 20 |
| Miscellaneous | |
| Sex: Female/male ratio (about 1:1.5) | |
| Incidence (about 1 in 10,000–20,000) |
Note. About 70% of PWS individuals have a partial deletion of chromosome 15 (15q11q13 region) that is donated by the father; about 25% have maternal uniparental disomy of chromosome 15 (both 15s from the mother); whereas the remaining 5% have other chromosome 15 abnormalities or genetic imprinting errors. These features are as summarized from the literature from over 500 reported PWS subjects by Butler in 1990.