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Chapter 155 Behçet Disease
Abraham Gedalia
Behçet disease is an autoinflammatory, multisystem disorder originally described as recurrent oral and genital ulceration associated with relapsing iritis or uveitis and is often characterized by cutaneous, arthritic, neurologic, vascular, and gastrointestinal manifestations.
The disease is reported commonly in the Mediterranean basin and Asia along the trading route, the so-called Silk Road, and is relatively rare in Europe and the USA. Among the populations of these areas, the estimated prevalence in adults ranges between 20 and 421/ 100,000, although in Europe the prevalence range is 0.6-6.4/100,000. The condition is uncommon in children, who account for an estimated 5% of cases. Most of the pediatric cases are diagnosed in late childhood, although disease symptoms may begin much earlier. On the basis of case reports and the later few series in children, the mean age of onset is 7.5 yr, and the mean age at which patients meet the diagnostic criteria for the diagnosis is 12 yr. The male : female ratio ranges from 1 : 1.2 to 1 : 1.4. No sex predominance is seen in adult-onset Behçet disease.
The etiology of Behçet disease is unknown, although both genetic and environmental factors may play a significant role in triggering the inflammatory process. Excessive T helper type 1 (Th1) cell activity and increased expression of heat shock proteins (especially HSP60) occur in patients with Behçet disease.
In areas of the world with a high prevalence of disease (along the old Silk Road), HLA-B51 allele located on chromosome 6p has been the most strongly associated risk factor. HLA-B51 may serve as an immunogenetic marker for a subgroup of patients with enhanced neutrophil function and eye involvement. A few cases of transient neonatal Behçet disease in offspring of mothers with the disease have been reported, suggesting that an antibody-mediated immune process may also have a role in the pathogenesis. The basic pathologic lesion is vasculitis of small and medium-sized arteries, with cellular infiltration leading to fibrinoid necrosis and narrowing and obliteration of the vessel lumens. Necrotizing and granulomatous inflammation of large vessels such as the aorta and pulmonary artery may also occur. There is speculation that Behçet disease is an autoinflammatory disease similar to sarcoidosis and inflammatory bowel disease and is caused by dysregulation of the innate immune system.
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