Lymphadenopathy in systemic lupus erythematosus: no microbial trigger found by shotgun metagenomics in a retrospective study on 38 patients.

Objectives: Lymphadenopathy is a classical manifestation of SLE flare, occurring in approximately half of patients during the course of the disease. Lymphadenopathy in SLE is frequently associated with fever. Microbial infection may play a role in SLE onset and flares. The objectives of this study were to describe lymphadenopathy in the course of SLE and identify potential infectious triggers using microbial metagenomic analysis.

Methods: We performed a retrospective monocentric study of 38 patients with SLE who had lymph node biopsy at baseline or during follow-up. Shotgun metagenomics were performed in the patient's lymph node biopsy to look for microbial RNA and/or DNA.

Results: Lymph node pathological analyses revealed follicular and/or paracortical hyperplasia in 73.7% of patients and histiocytic necrotizing lymphadenitis in 23.7%. At the time of biopsy, SLE patients exhibited fever in 29%, splenomegaly in 10%, cutaneous manifestations in 47%, polyarthritis in 32%, seritis in 13% and LN in 18%. Half of the patients (50%) had an increased CRP level, 35% had low C3, 65% had hypergammaglobulinemia. Microbial metagenomic analysis of lymph node biopsy revealed an absence of microbial DNA in 92% of patients, the presence of CMV in very small quantities in 2 patients, and the presence of HHV-7 in low quantities in a single patient.

Conclusion: Despite suggestion that certain microorganisms may play a role in the pathogenesis and flares of SLE, our microbial metagenomic analysis study did not highlight possible infectious triggering factors. Further and better-designed studies are needed to confirm these results.