Pediatric SLE includes monogenic forms, some of which involve the interferon type I (IFN-I) pathway. The IFN-I pathway is renally active in adult SLE and correlates with the extent of renal damage. In pediatric SLE, and particularly in lupus nephritis, activation of the IFN-I pathway has never been studied, nor is it known whether monogenic forms underlie more pronounced interferon activation.

Pediatric systemic lupus erythematosus (SLE) (cSLE), compared with adult SLE, is characterized by a more severe phenotype, with more marked hematologic, neuropsychiatric, and renal changes. Lupus nephritis is a pivotal manifestation of pediatric SLE and an important prognostic factor. It is hypothesized that activation of the interferon pathway is more pronounced in monogenic forms, in which the response to IFN-I represents the primary alteration and likely the main pathogenic mechanism.

This finding may also be relevant in light of the availability of new drugs that selectively target the IFN-I pathway.

Demonstration of IFN-I pathway activation could be used as a diagnostic algorithm in aggressive pediatric forms resistant to immunosuppressive therapy and represent a therapeutic target.

Inclusion Criteria:

• Diagnosis of SLE arising before the age of majority (until the age of 18 years) according to SLICC and/or EULAR criteria 2019;
• Clinical, laboratory and/or histologic evidence of renal involvement manifested before the age of 18 years;
• Signature of informed consent.

Exclusion Criteria:

• Onset of renal disease after the age of 18 years;
• SLE secondary to drugs or associated with other diseases such as systemic sclerosis, rheumatoid arthritis, Sjögren's syndrome, and other connectivities.