The case of a 35-year-old man with progressive dementia from the age of 17 is presented. Clinical examination showed mild extrapyramidal and cerebellar signs and rare myoclonus. Neuropsychological evaluation disclosed severe cognitive deficits. Magnetic resonance imaging (MRI) revealed moderate generalized atrophy with abnormal iron deposition in the basal ganglia. Positron emission tomography (PET) with 18-fluorodeoxyglucose (18-FDG) demonstrated clear temporoparietal hypometabolism. The clinical symptoms and course are typical for the rare adult type of neuronal ceroid lipofuscinoses (Kufs' disease). The diagnosis is supported by the electron microscope detection of an abnormal accumulation of lipid vacuoles and lipofuscin in the eccrine sweat glands and the rectal ganglia cells.