Presence of tubuloreticular inclusions in ultrastructural studies of renal biopsies in children with lupus nephropathy - one-center preliminary study.

Juvenile systemic lupus erythematosus (jSLE) is an autoimmune disease that develops as a result of multi-level immune dysregulation, including the interferon pathway. Nephropathy develops at an early stage and eventually affects 90% of patients. A renal biopsy allows one to classify lupus nephritis and determine the proper treatment. Biopsy assessment should be done not only in a light microscope but also in a transmission electron microscope (TEM). Its usage may reveal the presence of intracellular tubuloreticular inclusions (TRIs), considered as a morphological marker of interferon hyperactivity. Renal biopsies of 10 children with jSLE and nephropathy were analyzed in TEM. The location, structure, and size of TRIs were assessed. Demographic data, nephropathy manifestation, non-renal symptoms, and serological activity of lupus were analyzed. All the patients were female with an average onset at 12.7 years of age and met SLE criteria. Nephropathy manifested with proteinuria (n = 10) and hematuria (n = 6). Glomerular filtration rate (GFR) was normal in all patients. In three children with early disease onset, it manifested with hematological disorders. TRIs were revealed in 7 biopsies, with the highest expression in the youngest children, with peripheral cytopenia, membranous glomerulonephritis, and lupus nephritis. Demonstration of TRIs in renal biopsies of children with juvenile systemic lupus may confirm the diagnosis of lupus nephritis and is a sign of involvement of the interferon pathway at the early stage of the disease.