Objective: To investigate comprehensively the relationships between Behçet's disease (BD) clinical features and HLA-B51 or HLA-B5 (HLA-B51/B5) status using meta-analyses.

Methods: Relevant publications were identified by a systematic literature search. Eligible studies had to provide frequencies for one or more BD characteristics according to HLA-B51/B5 status. Pooled relative risks (RRs) were calculated by random-effects meta-analysis for those BD characteristics for which five or more relevant studies were identified. Between-study variability was assessed with I(2) and Q-statistics, and modelled using meta-regression.

Results: Among the 859 publications evaluated, 72 (representing 74 study populations) met eligibility criteria. Pooled RRs (95% CIs) of the association of HLA-B51/B5 with the 14 analysed clinical characteristics were male sex 1.14 (1.05, 1.23); eye involvement 1.13 (1.06, 1.21); genital ulcers 1.07 (1.01, 1.14); skin involvement 1.10 (1.03, 1.16); erythema nodosum 1.11 (0.96, 1.29); pseudofolliculitis 1.07 (0.93, 1.23); positive pathergy test 1.05 (0.94, 1.17); joint involvement 0.94 (0.86, 1.04); neurological involvement 0.95 (0.71, 1.27); gastrointestinal involvement 0.70 (0.52, 0.94); thrombophlebitis 1.17 (0.77, 1.76); vascular involvement 1.00 (0.68, 1.47); chest involvement 1.55 (0.75, 3.20) and orchiepididymitis 1.13 (0.59, 2.15). For most of the analysed outcomes, between-study heterogeneity was low or absent and most of the meta-regression models were statistically non-significant.

Conclusions: The results of these meta-analyses showed that, in BD, HLA-B51/B5 carriage predominates in males and is associated with moderately higher prevalences of genital ulcers, ocular and skin manifestations, and a decreased prevalence of gastrointestinal involvement.