Hughes-Stovin syndrome (HSS) preliminary diagnostic criteria: a paradigm shift in managing pulmonary vasculitis in HSS and Behçet's disease (BD). On behalf of the HSS International Study Group (HSSISG) : Reply on Tahir Saygın Öğüt and Veli Yazısız "Comments on the proposed diagnostic criteria for Hughes-Stovin syndrome: the role of Behçet syndrome" (CLRH-D-26-01350).

Hughes-Stovin syndrome (HSS) is a rare and aggressive type of systemic vasculitis which is characterized by peripheral venous thrombosis and pulmonary artery aneurysms (PAAs) at the onset of the disease, as well as the absence of recent or previous attacks of uveitis. The onset of HSS and its dominant clinical disease presentations differ in many aspects from those observed in Behçet's disease (BD). The absence of uveitis is a mandatory exclusion criterion in the preliminary diagnostic criteria proposed by the HSS International Study Group (HSSISG), to avoid misclassification between HSS and BD. The presence of PAAs is an obligatory "entry criterion" for diagnosis, while vascular thrombotic events are a "major criterion" after excluding other causes of coagulopathy-induced thrombosis. The HSSISG regards HSS and BD as one disease, yet exhibiting distinct patterns of disease expression, particularly at disease onset. Differentiating HSS from BD is especially important for early diagnosis and optimal management. While the presence of HLA-B51 is the strongest genetic risk factor for BD, it is not used as a criterion to confirm a diagnosis because it lacks sufficient specificity. The prevalence of HLA-B51 in HSS is relatively low, suggesting that different genetic drivers might exist or that HSS is a unique entity with overlapping features with BD. In HSS, both HLA-B51 positive and negative cases have been described; thus, it cannot be a hallmark of the syndrome, and it does not play a role in the diagnostic criteria.