8486 Age at diagnosis in Prader Willi Syndrome (PWS)

Abstract Disclosure: R. Sritharan: None. J. Lodge: None. S. Tadros: None. L. Menzies: None. E.F. Gevers: None. PWS is a complex neurodevelopmental disorder characterised by neonatal hypotonia,failure to thrive, hypothalamic and endocrine dysfunction, behavioural and learning difficulties and hyperphagia. It is caused by absence of expression of paternally imprinted genes on chromosome 15q11-q13. PWS is confirmed by genetic methylation analysis of this region. Most patients with PWS are referred for genetic investigations in the first months of life due to severe hypotonia and/or failure to thrive. However, it is known that some patients are still only diagnosed in adulthood, with resulting missed opportunities for prompt early treatments for PWS, such as growth hormone therapy. Little information is available on age of diagnosis of PWS, and whether opportunities to request genetic investigation are missed in childhood. We therefore aimed to study age at diagnosis of PWS in the UK. To do so, we assessed data as reported to the UK patient association PWSA-UK from 1968-2023, and additionally audited PWS genetic testing by the North Thames Genomics Laboratory Hub from 2019-22. Of 1145 people registered at PWSA as having PWS, 945 had an age of diagnosis recorded. Of these, 254 (28%) were diagnosed over 1 year of age. From March 2021 to Sept 2023, 13 were diagnosed over 1 year of age with a mean age at diagnosis of 9.27 yr (95% CI 4.15 to 14.4) and with 8 patients below 5 years of age. We assessed PWS diagnoses made in blocks of 4 years from 1968, and the number of PWS diagnoses in people over age 1 year in those time blocks. The number of diagnoses in people over 1 year of age appeared to decrease since 1996 to 7 but from 2015 this has been fluctuating. North Thames Genomics Laboratory Hub provides testing for around 10 million people in and around London. Over a 3-year period between 2019-2022, there were 59 requests for PWS testing. 28 of these were positive (a 47% diagnostic yield). 20/28 (71%) of patients were diagnosed under 1 month of age, 7% were diagnosed at 1-24 months of age, 3.5% at 2-5 yrs and 18% at >5 yrs of age (one at age 9, two at age 18, one at age 29 and one at 33 yrs of age). Most tests were performed in children under1 month of age (91% yield), followed by those over 5 yrs of age (30% yield). For 10 individuals, microarray was requested, however methylation studies would have been more appropriate. All patients diagnosed over 5 years of age had hypotonia and were described as hyperphagic and having intellectual disability, and 75% were obese. Patients diagnosed after age 8were described as having neonatal hypotonia and may have been eligible for genetic testing soon after birth. These data suggest that a considerable percentage of patients are diagnosed with PWS after the first year of life in the UK. Further root analysis, interventions, and education is required to reduce age at diagnosis in patients with PWS to allow for optimal management starting in the first few months of life. Presentation: 6/1/2024