Kidney Involvement in Autoinflammatory Diseases.

Background: Autoinflammatory diseases (AIDs) were first proposed 20 years ago and caused by dysregulation of the innate immune system, leading to episodes of systemic inflammation. Advances in next-generation sequencing and biological technology have resulted in the identification of new monogenic diseases and the corresponding signaling pathways that may guide us in targeted therapy. The kidney is a major target organ of various inflammatory processes. Summary: During systemic inflammation, increased pro-inflammatory cytokines, such as IL-6, IL-1β, and TNF, lead to over-transcription and release of acute phase reactant serum amyloid A (SAA). Sustained high SAA levels promote a cascade of pathophysiological events, including protein misfolding, protein fragmentation, and aggregation into highly ordered amyloid fibrils. Amyloid fibril deposition in the kidney cause progressive glomerular and vascular damage. Renal AA amyloidosis is a common and severe complication of AIDs, including familial Mediterranean fever, cryopyrin-associated periodic syndromes, TNF receptor-associated periodic fever syndrome, mevalonate kinase deficiency/hyper-IgD and periodic fever syndrome, and deficiency of adenosine deaminase 2. Amyloidosis may even be the first clinical manifestation in some patients, presenting with asymptomatic proteinuria, nephritic syndrome, progressive renal insufficiency, or end-stage kidney disease. In addition, major dysregulated pathways in different AIDs lead to endogenous inflammation, which is due to direct endothelial cytotoxicity caused by IL-1β, type I interferon, or possibly immune complexes. The kidney is frequently affected by various vasculitis, and kidney involvement is a major determinant of treatment options and outcomes. The renal vasculitis involved in AIDs includes renal artery Takayasu vasculitis, polyarteritis nodosa, and IgA vasculitis. Moreover, other kidney diseases, such as glomerulonephritis, lupus nephritis, and renal tubular dysfunction, were also reported in AIDs. Key Messages: Kidney manifestations can be a coexisting disease seen with AIDs. They may also be one of the characteristics of AIDs. Clinicians should be aware of the possibility that amyloidosis, vasculitis, or other kidney diseases may be associated with AIDs in order to make appropriate diagnosis and treatment. Kidney biopsy may be of great significance. Biologics, which switch off the underlying cytokine-mediated inflammatory process, have the potential to restore organ damage and improve the outcome in the very early stage of the disease.