RESUMEN
DNASE1L3 is an extracellular nuclease that digests chromatin released from apoptotic cells. DNASE1L3 mutations impair the enzyme function, enhance autoantibody production and type I interferon (IFN-I) responses, and cause different autosomal recessive phenotypes ranging from hypocomplementemic urticarial vasculitis syndrome to full-blown systemic lupus erythematosus (SLE). Kidney involvement in patients with DNASE1L3 mutations is poorly characterised. Herein, we describe the clinical course of three children with monogenic SLE due to DNASE1L3 mutations who developed refractory glomerulonephritis leading to kidney failure. They had different renal histopathological patterns (i.e., membranous, endo- and extra-capillary glomerulonephritis and thrombotic microangiopathy), all belonging to the lupus nephritis (LN) spectrum. One patient had a mixed phenotype, showing an overlap between SLE and ANCA-associated vasculitis. Using immunofluorescence, we detected glomerular expression of the IFN I-induced human myxovirus resistance protein 1 (MXA), which was particularly evident in glomerular endothelial cells. 2/3 patients had increased expression of interferon-stimulated genes in the peripheral blood and all three patients had reduced serum DNAse activity. Our findings suggest that DNASE1L3-related glomerulonephritis can be included in the spectrum of IFN I-mediated kidney disorders, and provide the rationale for IFN I-directed therapies in order to improve the poor outcome of this rare condition.
RESUMEN
Early-onset systemic lupus erythematous (SLE) is a distinct clinical entity characterized by the onset of disease manifestations during childhood. Despite some similarities to patients who are diagnosed during adulthood, early-onset SLE typically displays a greater disease severity, with aggressive multiorgan involvement, lower responsiveness to classical therapies, and more frequent flares. Lupus nephritis is one of the most severe complications of SLE and represents a major risk factor for long-term morbidity and mortality, especially in children. This review focuses on the clinical and histological aspects of early-onset lupus nephritis, aiming at highlighting relevant differences with adult patients, emphasizing long-term outcomes and discussing the management of long-term complications. We also discuss monogenic lupus, a spectrum of conditions caused by single gene variants affecting the complement cascade, extracellular and intracellular nucleic acid sensing and processing, and occasionally other metabolic pathways. These monogenic forms typically develop early in life and often have clinical manifestations that resemble sporadic SLE, whereas their response to standard treatments is poor.