Objective Hematological manifestations of systemic lupus erythematosus (SLE) are frequently observed, but neutropenia is less common and is not included in the classification criteria. Still, neutropenia is a risk factor for infections, especially those caused by bacteria or fungi. Herein, we aimed to systematically evaluate all infections in a large SLE cohort and especially in subjects with neutropenia.

Methods Longitudinal clinical and laboratory parameters obtained at visits to the Rheumatology Unit, Linköping University Hospital, Sweden, and linked medical data were assessed from all subjects included 2008–2022 in our regional register. Data on confirmed infections were retrieved from medical records and carefully reviewed.

Results A total of 333 patients were included and monitored at 3088 visits during the study period. In total, 918 infections were identified and 94 occasions with neutropenia (<1.5×109/L) were detected in 40 subjects (12%). 30 neutropenic episodes in 15 patients occurred in association with infections, of which 13 (43%) required in-hospital care, 4 (13%) needed intensive care and 1 (3%) resulted in death. Bayesian analysis showed that patients with ≥1 occasion of neutropenia were more likely to experience ≥1 infection (OR=2.05; POA=96%). Invasiveness and severity of the infections were significantly associated with neutropenia.

Conclusions Infections were common among Swedish patients with SLE and 12% showed neutropenia over time. Nevertheless, confirmed neutropenia co-appearing with infections appears to be associated with both invasiveness and severity whereas lymphopenia and hypocomplementemia do not seem to be as important. Importantly, the presence of neutropenia was linked to both invasiveness and severity of infections. Awareness of the risks of severe infections in neutropenic patients with SLE is crucial in order to tailor therapy to avoid severe illness and death.