Abstract: INTRODUCTION: There is a wide range of non-specific symptoms that can reveal neurolupus, sometimes making diagnosis difficult. OBSERVATION: A 29-year-old man presented, from 1996 to 2002, three episodes of mood disorders with hetero-aggression, preceded by seizures, which resolved completely. Repeated investigations were negative except for lymphopenia, an inflammatory cerebrospinal fluid and some rare non-specific areas of high intensity signals in the white matter on the brain MRI. After a six-year course, the patient was considered to have a severe mood disorder related to a schizoid personality. A new dot-blot search for antinuclear antibodies detected anti-Sm antibodies was positive, leading to the diagnosis of neuropsychiatric lupus since the patient's symptoms fulfilling four of the American Rheumatism Association criteria (neuropsychiatric events, lymphopenia, antinuclear and anti-Sm antibodies). The patient was given monthly pulses of cyclophosphamide and remained symptom free one year after the last flare up. CONCLUSIONS: Lupus can rarely be revealed by long-standing isolated psychiatric disorders. Search for auto-antibodies, using highly specialized techniques (western blot, dot blot) should be a routine practice since antibody titres fluctuate during the course of the disease; elevated titres may correlate with exacerbations. Considering the prominence and severity of these behavior disorders, systemic diseases may often be misdiagnosed.