[Hereditary metabolic diseases with onset in adulthood. Early and correct treatment of acute symptoms can be life-saving].

Inherited metabolic diseases usually present in the neonatal period or before school age. A growing portion of the disorders can be treated successfully, and an increasing number of patients are now treated in adult medicine. Several of the disorders also exist as attenuated variants without distinct symptoms in childhood. They can present as an acute onset event during metabolic stress in adulthood. We describe three patients with acute clinical decompensation in adulthood with severe sequelae and propose investigations to help diagnose such patients. One patient was unconscious from ammonia intoxication and developed severe neurological sequelae because of a defect in the urea cycle. A second patient had seizures caused by a defect in the conversion of homocysteine to methionine, resulting in lack of S-adenosylmethionine. A third patient had a stroke and grossly elevated homocysteine caused by undiagnosed homocystinuria. Recently there have been dramatic improvements in diagnostic methods, and new therapies are continuously being developed. Knowledge of these disorders is therefore of increasing importance also in adult medicine.