Oast house urine syndrome An extremely rare condition in which there is an inability to absorb methionine (an important amino acid) from the gut. This leads to the collection of abnormal substances in the blood and their excretion in the urine which has a distinctive smell resembling dried celery, burnt sugar or an oast house. Affected children have fine hair, blue eyes and episodes of overbreathing and diarrhoea. Severe mental handicap and epilepsy are present. The early introduction of a low methionine diet may improve physical and mental development. The condition is probably inherited from both parents who are carriers (recessive inheritance).