Hi Nivv, I dont have PKu but I work with a gentleman in his 60s who was born before the Guthrie test was introduced for all new born babies. I help look after him with a team of support staff. nPrior to living where he is now he was in a long term institution for people with learning disabilities and before that he was cared for athome by his mum until she died. nWe dont have access to his past medical history bur he hasnt been on a diet for at least the last 7years although that has changed recently. nHe used to be very lethargic, uninterested in most things and moody and often presented challenging and difficult behaviour. nHe is also medicated (long term) with major tranquilisers. nSince being referred to the dietician ( who normally works with babies and yopung adults) he has become a new man. nHe appears happier,more cooperative, less moody ,More physically active and in general much happier with life. nHis IQ will never improve but I believe that by being on a low PHe diet his quality of life has improved tremendously. nWishing you and your brother best wishes.