Prevalence of Adamantiades-Behçet's disease in Germany and the municipality of Berlin: results of a nationwide survey.

Sirs, The worldwide prevalence of Adamantiades-Behçet’s disease (ABD) has been estimated to be in the range of 0.12 420 per 100.000 inhabitants, the highest assessed in Istanbul, Turkey (1) and the lowest in the U.S.A. (2). This considerable difference is likely to be genetically determined as further suggested by occasional familial cases and in association with HLA haplotypes, such as HLA-B51; though it remains unclear whether exogenous agents trigger the disease (3). The current prevalence of ABD in Germany based on data of the German registry that has been established in 1990 was higher than previous reports not only among native Germans but also among other ethnic groups. The 2005 survey estimated a prevalence of ABD in Germany of 0.72: 100.000 and in the municipality of Berlin of 4.87: 100.000. This current increase, however, is still in the range of ABD prevalence in other Northand West-European countries (4, 5). From the registered 590 patients (344 male and 246 female), 522 patients fulfilled the criteria of ABD classification tree (6), 63 additional patients fulfilled Cheng and Zhang’s criteria (4 complete and 59 incomplete) (7), one additional patient fulfilled Dilsen’s criteria (8), and 4 patients were diagnosed clinically in the initial stage of the disease only presenting recurrent oral aphthae. The patients belonged to 31 ethnic groups: 267 were of Turkish origin, followed by patients of German (n = 227), Greek (n = 10), Italian (n = 10), Lebanese (n = 10), Serbian and Montenegrin (n = 9), Vietnamese (n = 5), Moroccan (n = 5) and other, less frequent origin (n = 49). Of the 165 ABD patients registered in the municipality of Berlin, the patients of Turkish origin constituted the larger ethnic group (n = 91), followed by patients of German (n = 43), Lebanese (n = 8), Greek (n = 4), Italian (n = 3) and other origin (n = 16). The current nationwide prevalence of ABD among the German population is 0.30 per 100.000, whereas in Berlin it is 1.47: 100.000. The highest ethnic prevalence was that of patients of Turkish origin (nationwide 15.13: 100.000; in Berlin 77.37: 100.000), as well as by patients of Lebanese (nationwide 24.46: 100.000; in Berlin 101.32:100,000) and Greek origin (nationwide 3.16: 100.000; in Berlin 39.73: 100.000). Previous reports of ABD prevalence in Berlin, the city with the highest number of non-native German inhabitants, have showen lower rates (Table I). Although there was an increase of ABD prevalence in all ethnic groups, the most striking increase is among non-native Germans, mainly among Turks. Interestingly, the current prevalence in Berlin among patients of Turkish origin has approached that of Western Turkey (20-80: 100.000) (9). It is likely that this increase is not only due to new cases from all ethnic groups but also to increased awareness for the disease. Furthermore, most of the ABD patients ethnic groups (Turks, Lebanese, Kurds, Kazakhs, Kyrgyz, Iranians, Afghans, Indians, Pakistanis, etc.) represent those living along the historical “silk road” thus favouring the genetic aetiology of the disease rather than environmental factors (10). The patients of Turkish origin exhibited an androtropism with a male-to-female ratio of 1.9 (175 males and 92 females), whereas male patients only were registered in a few other ethnic groups from Southern European and the Middle East. German patients exhibited an almost equal male-to-female ratio (119 females and 108 males); ethnic groups of Far East, such as Koreans and Vietnamese only included female ABD patients. Obviously the historical ABD androtropism seems to vanish as surveys become larger and carried out nationwide. Indeed, in surveys with large numbers of ABD patients, no gender prevalence was assessed. In conclusion, the prevalence of ABD in Germany calculated in this study is higher than in earlier reports but it still ranks among the prevalence in other north-western European populations. The prevalence of ABD in Berlin is the highest nationwide, due to the multi-ethnic character of the urban Berlin population. The observed prevalence in patients of Turkish origin living in Germany was similar to that reported from Western Turkey. This finding disputes previous concepts of an environmental triggering factor and corroborates the major role of a genetic background in ABD pathogenesis.