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Age at onset of inappropriate weight gain in prader-Willi syndrome; an opportunity for obesity prevention
  1. N Abouof,
  2. M Donaldson,
  3. M Guftar Shaikh
  1. Department of Endocrinology, Royal Hospital for Sick Children, Glasgow, UK


Background Prader-Willi Syndrome (PWS) results from loss of paternally imprinted gene (s) from the 15q 11-13 region and is characterised by weight faltering during early childhood due to hypotonia, followed by obesity due to onset of the hyperphagic phase.

Aim of study (1) To determine the presence of an age zone during which excess1 weight gain is particularly likely, in order to target counselling and dietary input. (2) To identify any possible factors that may contribute in the onset of the excessive weight gain.

Method Body Mass Index (BMI) was calculated for each data point in 40 patients with PWS (M=24, F=16) from a single centre seen over a 20-year period. Two researchers independently scrutinised the chart for each patient and to estimate or identify the age at which an inappropriate rise in BMI began.

Results 76 patients were identified of which 36 had insufficient data for analysis leaving 40 for study. No inappropriate increase in BMI trend occurred in (10 patients), at last data point 5.3 (1.5-15.2) years. Age at BMI increase could not be ascertained in 9 patients, all of whom became obese (BMI SDS >2) by 3.2 (2-5) years. Of 21 patients in whom age at BMI increase could be estimated (8 patients) or precisely identified (13 patients) the median age at the time of increase was 2 (0.5-3.8) years with 18/21 patients showing onset of increase between 1 and 2 years of age. Significant negative correlation between age of transition and term of gestation (r=−0.530), gestational age (r=−0.530) and birth weight (r=−0.416) was found from all the measured variables.

Conclusion The critical age of excessive BMI increase in most PWS subjects is between 1 and 2 years, regardless the measured factors except of birth weight and Gestational age, suggesting other underlying path-physiological factors. Structured input from a multidisciplinary team should be intensified at one year of life to pre-empt this trend.

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