[Update on Behçet syndrome].

Background: Behçet syndrome (BS) is a vasculitis of variable vessels with multiple organ manifestations.

Objective: This article gives an overview of innovations in the last 2 years.

Material and methods: A literature search was carried out using the keyword "Behcet" in 2022-2024 in PubMed. The selection of suitable articles was based on the relevance.

Results and conclusion: With respect to the pathophysiology it is now clear that BS occupies an intermediate position between autoinflammatory and autoimmune clinical pictures. It is now classified as MHC-I-opathy, i.e., a disease that has a strong association with HLA class I antigens, which also play a prominent role in the pathogenesis. The diagnostic international criteria for Behcet's disease (ICBD) from 2014 with a score of 4 points or more that makes the diagnosis of BS probable have become established; however, in countries with a low prevalence of BS, the differential diagnosis of BS from other diseases is difficult and a higher point limit in the diagnostic score seems to make sense in order to avoid incorrect diagnoses. Clusters or phenotypes of the disease have now been described in various countries in which different symptom complexes frequently occur together; however, the clusters differ between the different countries of origin and depending on the age of the patients. Sonography of the common femoral vein with specific wall thickening in BS patients has been established as an additional tool for the differential diagnosis. Typical characteristics of oral aphthae in BS were also described and the frequency of positivity in the pathergy test could be significantly increased using pneumococcal antigens as the reagent. The treatment recommendations of the EULAR from 2018 still apply; in treatment-refractory cases, tocilizumab, secukinumab, Janus kinase inhibitors (JAKi) and ustekinumab have now also been successfully used. The new EULAR treatment recommendations are expected in 2025.