Summary
Behçet's disease (BD) is a systemic inflammatory disease of unknown origin. It mainly occurs in young adults, who present with muco-cutaneous signs, such as oral or genital aphthae, necrotic folliculitis and erythema nodosum. Systemic manifestations have been described and include ocular (uveitis, retinal vasculitis), neurological (encephalomyelitis, meningitis, intracranial hypertension, behaviour disorders), vascular (venous and/or arterial thromboses, arterial aneurysms) but also articular, digestive and renal manifestations. BD is more frequent in a geographic area stretching from Eastern Asia to the Mediterranean region. The mean prevalence is estimated at 1/13 300. The disease usually starts between 18 and 40 years, but paediatric cases have been reported. Painful oral aphthous ulcers are present in 98% of the cases. Genital ulcers, observed in 60-65% of cases, are highly evocative of BD. Ocular involvement is frequent (50-70%) and severe, potentially leading to blindness. Venous involvement (30% of cases) essentially results in thromboses in femoro-iliac, superior and inferior vena cava and cerebral territories. Arterial involvement (3-5% of cases) predominantly affects pulmonary vessels. It is a main cause of mortality due to the occurrence of thromboses or aneurysm rupture. Arthralgia and/or arthritis are frequent (45%) and can occur as a initial symptom. Neurological involvement (Neuro-Behçet Disease or Neuro-BD), present in 20% of cases, can occur 1-10 years after the first symptoms. Aphthoid and/or ulcerative lesions can affect the whole digestive tract, but preferably involve the cæcum and ascending colon. Serious complications can occur, such as haemorrhages and perforations. The aetiology of BD is multifactorial. A combined role of environmental factors, such as viruses or bacteria and of genetic factors is likely. Their respective contribution could play a determining role in the expression of the disease and especially the age of onset, as the role of genetic factors seems stronger in the development of paediatric forms. The HLAB5101 antigen is associated to BD in 50-70% of patients, mostly from Asiatic or Mediterranean origin. The unpredictable evolution of BD, involving inflammatory attacks without any apparent triggering factor, shows some similarity to that of the group of auto-inflammatory disorders. This hypothesis is strengthened by the likely implication of the MEFV gene (responsible for familial Mediterranean fever) and TNFR gene (responsible for TRAPS syndrome) on the occurrence of some BD clinical manifestations (such as vasculitis). BD diagnosis is difficult to establish, due to the absence of pathognomonic sign. Nevertheless, some organ involvement can be very typical (such as uveitis) and strongly evoke BD diagnosis. Differential diagnosis includes Crohn's disease, and in paediatric forms, the hyper IgD syndrome (HIDS, mevalonate kinase deficiency). Treatment is symptomatic, and consists of steroids and immunosuppressants. Biotherapies are used in the treatment of the most severe manifestations (especially ocular). Treatment is effective only when rapidly prescribed and at efficacious doses. Patient's adhesion to treatment, duration of therapy and experience of the medical team are also important. In the absence of treatment, the prognosis is severe due to ocular involvement leading potentially to blindness, to the risk of arterial rupture and to neurological involvement potentially causing encephalopathy, pseudo-bulbar syndrome or dementia with loss of autonomy. *Author: Pr I. Koné-Paut (October 2006)*.
