Complement 3 Glomerulonephritis is an Overlap Lupus-Sjögren Syndrome: A Case Report

We herein report a case of a 47-year-old male, with symptoms of thoracic pain and recent history of evanescent malar rash, diffuse migratory polyarthralgia, oral and ocular dryness. Laboratory results showed acute kidney injury and positivity for anti-nuclear, anti-DNA, anti-Ro and anti-LA antibodies. Study led to diagnosis of overlap systemic lupus erythematosus (SLE) and Sjögren’s syndrome (SS). Results of kidney biopsy presented an exclusivity of C3 in immunofluorescence, consistent with histopathological diagnosis of Complement 3 glomerulopathy. Renal involvement of SLE classically involves an immune complex-mediated glomerulonephritis which is known to activate classical pathway of complement. On the other hand, C3 glomerulopathy is a rare kidney disease characterized by dysregulation of the alternative pathway of the complement system. Previous described cases that correlated C3 glomerulopathy and autoimmune disease presented genetic alterations. The genetic study of our patient, however, did not identify any pathogenic genetic variables in complement genes. We provide a review of current evidence in the search for other the pathophysiological mechanisms that may provide an answer as to why this case happened. To our knowledge this is the first described case of overlap SLE-SS with histological findings of C3 glomerulopathy. All authors declare they have no conflict of interest.

Keywords: Complement 3 glomerulopathy, Systemic Lupus Erythematosus, Sjögren’s Syndrome.