COMPARISON OF PHENOTYPE IN UNIPARENTAL DISOMY AND DELETION PRADER-WILLI-SYNDROME - SEX-SPECIFIC DIFFERENCES

Prader-Willi syndrome (PWS) results primarily from either a paternal d eletion of 15q11-q13 or maternal uniparental disomy (UPD) 15. Birth pa rameters and clinical presentation of 79 confirmed UPD cases and 43 de letion patients were compared in order to test whether any manifestati ons differ between the two groups. There were no major clinical differ ences between the two classes analyzed as a whole, other than the pres ence of hypopigmentation predominantly in the deletion group. However, there was a significant bias in sex-ratio (P<.001) limited to the UPD group with a predominance (68%) of males. An equal number of males an d females was observed in the deletion group. When analyzed by sex, se veral significant differences between the UPD and deletion groups were observed. Female UPD patients were found to be less severely affected than female deletion patients in terms of length of gavage feeding an d a later onset of hyperphagia. Although these traits are likely to be influenced by external factors, they may reflect a milder presentatio n of female UPD patients which could explain the observed sex bias by causing under-ascertainment of female UPD. Alternatively there may be an effect of sex on either early trisomy 15 survival or the probabilit y of somatic loss of a chromosome from a trisomic conceptus. (C) 1996 Wiley-Liss, Inc.