INTRODUCTION: The ability to degrade neutrophil extracellular traps (NETs) is 
reduced in a subset of patients with systemic lupus erythematosus (SLE). NETs 
consist of chromatin covered with antimicrobial enzymes and are normally 
degraded by DNase-I, an enzyme which is known to have reduced activity in SLE. 
Decreased ability to degrade NETs is associated with disease activity. In the 
current study we investigated how the ability of serum from SLE patients to 
degrade NETs varies during the course of SLE as well as what impact this may 
have for the clinical phenotype of SLE.
METHODS: Serum from 69 patients with SLE, included in a prospective study, was 
taken every 60 days for a median of 784 days. The ability of serum to degrade 
NETs was determined and associated with clinical parameters occurring before and 
at the time of sampling, as well as after sampling by using conditional logistic 
regression.
RESULTS: As many as 41% of all patients in the study showed decreased ability to 
degrade NETs at least once, but with a median of 20% of all time points. 
Decreased degradation was associated with manifestations of glomerulonephritis 
as well as low complement levels and elevated levels of antibodies directed 
against histones and DNA. Furthermore, the odds ratio for the patient to develop 
alopecia and fever after an episode of decreased NETs degradation was increased 
by four to five times compared to normal.
CONCLUSIONS: Decreased degradation of NETs is associated with clinical 
manifestations in SLE and may contribute to disease pathogenesis. Potential 
therapeutics restoring the ability to degrade NETs could be beneficial for 
certain patients with SLE.