Investigating the presence of neutrophil extracellular traps in cutaneous lesions of different subtypes of lupus erythematosus

Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of systemic lupus erythematosus (SLE). However, little is known about the implication of NETs in cutaneous lupus. In this case series of 30 patients, we compared the amounts of neutrophils producing NETs in cutaneous lesions of different subtypes of lupus (5 with discoid lupus or DLE, 5 with subacute cutaneous lupus or SCLE, 11 with acute cutaneous SLE, 7 with lupus panniculitis and 2 with chilblains). Immunofluorescence was performed on formalin-fixed paraffin-embedded skin biopsies using antibodies against neutrophilic granules (elastase, myeloperoxidase, PR-3 proteins and citrullinated histone 3). Dihydroethidium staining was performed to detect reactive oxygen species (ROS), known inducers of NETs. NETs were detected in the different subtypes of cutaneous lupus as well as in cutaneous lesions of SLE. The amounts of neutrophils producing NETs were significantly higher in lupus panniculitis (49%), acute cutaneous SLE (41%) and DLE (32%), in comparison with SCLE (5%) and chilblains (0%). This suggests that NETs might be associated with more tissue damage and scarring. ROS were observed in the different cutaneous subtypes of lupus independent of NETs.