Fever in systemic lupus erythematosus: associated clinical features and genetic factors.

Objectives: Fever has been recently included in the new 2019 EULAR/ACR classification criteria for systemic lupus erythematosus (SLE). Thus, we investigated the possible association of fever with other clinical disease manifestations. Then, we analysed a panel of 30 SNPs to verify their possible contribution to the pathogenesis of this constitutional symptom.

Methods: In this retrospective study we collected clinical/laboratory features in a SLE cohort, including the occurrence of fever (body temperature >37.5°C, excluding infective aetiology). A phenotype-genotype correlation analysis was carried out.

Results: We evaluated 167 patients (M/F 12/155, median age at the disease diagnosis 30 years, IQR 17; median disease duration 240 months, IQR 156). Seventy patients (41.9%) reported fever, significantly associated with: serositis and haematological manifestations (p=0.02 and p=0.00001, respectively). A significant association between fever and leukopenia (p=0.003), haemolytic anaemia (p=0.04), and thrombocytopenia (p=0.04) was observed. In addition, significantly higher median SLICC Damage Index (SDI) values were observed in patients with fever in comparison with those without [2 (IQR 3) vs. 1 (IQR 2); p=0.005]. The genotype/phenotype analysis showed an association between fever and the rs13361189 of Immunity Related GTPase M (IRGM) gene (p=0.003; OR 3.89, CI 1.16-13.03), confirmed also in multivariate logistic regression analysis (p=0.028, B=1.39).

Conclusions: The association between IRGM rs13361189 polymorphism and the occurrence of inflammatory fever, could provide new insights into the role of genetic background in the pathogenesis of this SLE-related feature.