The comprehensive assessment of a psychiatric case requires evaluating the symptoms from a comprehensive perspective, without bias, and suspecting unlikely pathologies where appropriate. We emphasize this from a case of Wilson's disease in which, as is frequent, the diagnosis was late. Clinical case: 36 year-old woman who from the age of 18 presented depressive and later psychotic symptoms, and her diagnosis was paranoid schizophrenia. The three-year diagnostic delay led to a poor evolution with permanent disabilities. The biased diagnostic attribution about parkinsonism as secondary to antipsychotics clouded the adequate diagnostic evaluation. Our case shows the need for a comprehensive neuropsychiatric perspective in the diagnostic evaluation. In a first case of psychosis, Wilson's disease should be considered within the differential diagnosis.