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

Introduction: 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.

Material and methods: 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.

Results: 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.

Conclusions: 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.