BACKGROUND: Behأ§et's disease is a multisystem vasculitis of unknown origin. The prevalence of the disease varies widely and is high in the Eastern Mediterranean Basin, North Africa, Iran and Japan. Many clinical features of Behأ§et's disease have been described and the international study group for Behأ§et's disease has defined a set of diagnostic criteriThese require the presence of recurrent oral ulcers plus two of the following: recurrent genital ulcerations, typical defined eye lesions, typical defined skin lesions or a positive pathergy test (a skin hypersensitivity reaction to a non-specific physical insult; when positive, the response consists of a papule or pustule that develops after 24 to 48 hours at the site of a needle prick to the skin). Although not included in these diagnostic criteria, there are some other features commonly seen in patients with Behأ§et's disease: thrombophlebitis, oligo-arthritis, gastrointestinal ulcerations and neurological involvement. Neuro-Behأ§et is well described in Behأ§et's disease, with variable prevalence rates between 5.3 and 35%. This prevalence is probably affected by the type of study (retrospective or prospective) and regional and ethnic variations in disease expression. Psychiatric symptoms usually occur as incidental findings in some patients with neurological disease; they are misdiagnosed and mistreated. CASE-REPORT: The patient described here developed acute psychotic symptoms without parenchymal cerebral involvement, and negative symptoms during Behأ§et's disease. Two hypotheses were evoked: schizophrenia associated with Behأ§et's disease versus psychiatric syndrome induced by vasculitis. Such a case has not been reported in the literature. We describe the case of a 31-year-old Haitian female, admitted because of an acute psychosis. She developed hallucination, misrecognition, psychomotor hyperactivity and delusion about her million childbirths. The patient had three years history of mistreated Behأ§et's disease, in particular recurrent oral ulcers, iritis and cardiovascular manifestations. She also had a history of uterine tumour, rectal carcinoid tumour and recurrent pleurisies. One year ago, she presented breast lymphangitis, anxiety, unusual thought content, hostility, suspiciousness, and poor impulse control: cranial computerised tomography scan was normal. After ten days of hospitalization, she complained of oral and genital aphta and no neurological sign was found. The cerebral angiographic magnetic resonance imaging showed a thrombophlebitis of the left lateral sinus without parenchymal involvement. Haloperidol, Heparin, Colchicine, Cyclophosphamide and Prednisone were introduced. Six months after, delirium and Behأ§et's symptoms had disappeared with the following treatment: Risperidone, Alprazolam, Zolpidem, Colchicine, Prednisone, and Azathioprine. The patient has developed enduring negative symptoms: blunted affect, social withdrawal, difficulty in abstract thinking, lack of spontaneity and flow of conversation and poor rapport. They are still present. This patient had two acute psychotic symptoms without parenchymal pattern. After treatment, she had persistent negative symptoms and psychosocial deterioration. This evolution is commonly seen in schizophreniDISCUSSION: Retrospective analysis of this patient's course suggests that -psychiatric episodes were always associated with physical manifestations. However, pleurisies, lymphangitis, uterine and rectal tumours have never been described in Behأ§et's disease. This vasculitis occurs less frequently in the Caribbean than in Mediterranean, Middle East or Japan. It seemed that this patient had a psychotic syndrome and a chronic relapsing multisystem disorder, more complex than Behأ§et's disease. A prospective study would be useful to characterize psychiatric patterns of Behأ§et's disease and establish their relationships with physical manifestations, especia