Behcet's disease (BD) is classified among vasculitides. There are actually five nationwide surveys of BD: Iran, Japan, China, Korea, and Germany. Among case series, four are on more than 200 cases (Turkey, Morocco, Tunisia, and UK). BD was classically seen around the Silk Route. Now, it is seen everywhere. The male to female ratios were, respectively (in nationwide surveys), 1.19, 0.98, 1.34, 0.63, and 1.40 to 1. The mean age at onset was 26.2, 35.7, 33.8, 29, and 26 years. Major manifestations were seen, respectively, in nationwide surveys: mucous membrane (oral aphthosis in 97%, 98%, 98%, 99%, and 98%; genital aphthosis in 65%, 73%, 76%, 83%, and 64%); skin manifestations (pseudo-folliculitis in 57%, N/A, 31%, N/A, and 62%; erythema nodosum in 22%, N/A, 38%, N/A, and 42%; ocular manifestations in 55%, 69%, 35%, 51%, and 53%). Minor manifestations were seen, respectively, in nationwide surveys: joint manifestations in 33%, 57%, 30%, 38%, and 53%; neurological manifestations in 9%, 11%, 6.5%, 4.6%, and 11%; gastrointestinal manifestations in 7%, 15.5%, 9%, 7.3%, and 12%; vascular involvement in 8.9%, 8.9%, 7.7%, 1.8%, and 13%; pulmonary manifestations in 0.3%, N/A, 2.2%, N/A, and 3.6%; cardiac manifestations in 0.5%, N/A, 4%, N/A, and 3.2%. Laboratory tests are not useful except the pathergy test, which was positive in 54%, 44%, N/A, 40%, and 34% of cases. ESR was normal in many patients. Diagnosis is based upon clinical manifestations. The International Criteria for Behcet's Disease (ICBD, 2006) may be of help, having a sensitivity of 98.2% and a specificity of 95.6% in Iranian patients.

Behcet's Disease (BD) is classified among vasculitides. The aim of this review was to put together different known reports in order to help the reader to better understand the disease, to avoid the frequent misdiagnosis, and to decide the best treatment. Areas covered: a) Epidemiology: BD is rare, and is seen along the Silk Road, from 20 to 420/100,000 in Turkey and 80/100,000 in Iran, to 0.64/100,000 in the UK. b) Clinical manifestations: oral aphthosis is seen in more than 95% of patients, genital aphthosis (60-90%), skin (pseudofolliculitis/erythema nodosum, 40-90%), eyes (uveitis/retinal vasculitis, 45-90%), gastrointestinal (diarrhea/hemorrhage/perforation/pain, 4-38%), vascular (venous/arterial thrombosis, aneurysm, 2.2-50%), neurological (all kinds, especially meningo-encephalitis, 2.3-38.5%), and articular (arthralgia/arthritis/ankylosing spondylitis, 11.6-93%). c) Pathergy test is positive in some patients: 8.6% (in India) to 70.7% (in China). This data was extracted from the five nationwide surveys and the largest case series from BD conference reports and a Pubmed search. Expert commentary: Diagnosis is clinical but classification/diagnosis criteria may help. The best criteria for BD is the International Criteria for Behcet's Disease (ICBD). BD is a multisystem disease progressing by attacks and remissions. Each attack may resemble the preceding or it may be different in duration, severity, and the systems involved.

Behcet's disease is mainly seen in young people. The most frequent symptoms are mucocutaneous, ocular and joint manifestations. Comparison with large series did not show major differences.

Rituximab was efficient in severe ocular manifestations of BD, TADAI improved significantly after 6 months with rituximab, but not with CCT.

Pathergy test (PT) is used for the diagnosis of Behcet's disease (BD). It is a criterion in many classification/diagnosis criteria. PT is mainly seen in BD but can be seen in other conditions too. PT has been reported with high frequency from most countries along the Silk Road. The sensitivity of pathergy phenomenon (PP) is declining over the time. The aim of this study was to look for the diagnostic value of PT in the past and at the present time. The BD registry (Rheumatology Research Center, Tehran University of Medical Sciences) has the data of 6,607 BD and 4,292 control patients. Patients and controls were divided in four groups of 1,650 BD and 1,073 controls. Sensitivity, specificity, positive and negative predictive value (PPV-NPV), positive and negative likelihood ratio (PLR-NLR), diagnostic odds ratio (DOR), and Youden's index (YI) were calculated for each group. The first and the fourth quartiles were compared. Sensitivity of PT decreased from 64.2% (first quartile) to 35.8% (fourth quartile). Specificity improved from 86.6% to 98.4%. PPV improved from 82.7% to 95.7%. NPV decreased from 82.7% to 60.5%. PLR improved from 4.8 to 22.4, while NLR deteriorated from 0.41 to 0.65. DOR improved from 11.6 to 34.3. Yuden's index worsened from 0.5 to 0.34. Although sensitivity of PP decreased, the increase of specificity is a plus value for diagnosis. As a result, PPV, PLR, and DOR improved, while NPR, NLR, and YI deteriorated. Although the pathergy test lost its sensitivity during the past 35 years, it has not lost its value as a diagnostic test, improving many of its characteristics. In a practical view, the chances of getting a positive test have decreased over the time. However, a positive test is rather the synonym of Behcet's disease, with a probability of 98.4%.

Introduction: This is an analysis of adult Behcet's disease (BD) in Iran, from the Iran Registry of 7187 BD patients, gathered from 1975 to 2014, among which 6075 were adults (84.5%).

There are 17 sets of diagnosis/classification criteria for Behcet's disease: Curth (1946), Hewitt (1969), Mason (1971), Japan (1972), Hubault (1974), O'Duffy (1974), Cheng (1980), Dilsen (1986), Japan revised criteria (1988), International Study Group on Behcet's disease (ISG criteria, 1990) . ISG criteria has very good specificity, but lacks good sensitivity and accuracy. In contrast, ICBD has much better sensitivity, a little less specificity and better accuracy.

ICBD has by far better performance than ISG in Iran. The difference is even more prominent in Iranian patients than in the cohort of the international patients upon whom the criteria were created.