Pauci-immune crescentic glomerulonephritis caused to dilemma in a patient with suspected systemic lupus erythematosus: a case report.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease and there is a distinct differentiation of clinical manifestations. Lupus nephritis (LN) is clinically apparent in approximately half of patients. A kidney biopsy is essential to define the kidney injury, exclude other injurious causes, and determine the histopathologic subtypes. Autoantibodies are crucial to the pathogenesis and the deposition of immune complexes in glomeruli is a hallmark of LN. The histopathology of LN is quite varied. Despite pauci-immune LN being an unexpected condition in SLE, it has been observed rarely with the presence of antineutrophil cytoplasmic autoantibodies (ANCA). We present a young male who was admitted to the emergency with syncope. The brain imaging revealed small infarct areas and signs of cerebral vasculitis. Also, he had elevated inflammatory markers, moderate proteinuria, and preserved kidney function. Anti-nuclear antibodies and anti-dsDNA were positive. Pauci-immune crescentic glomerulonephritis (PICGN) was observed in a kidney biopsy, however, ANCA was negative. SLE diagnosis was established by neurological manifestation, specific antibodies, proteinuria, and kidney biopsy findings. We administered a combination induction regimen, including pulse steroid and parenteral cyclophosphamide. The proteinuria was resolved in the follow-up. Our case highlights that SLE-associated ANCA-negative PICGN can be the initial presentation in the absence of typical manifestations. LN exhibits various pathological mechanisms in the kidney. As a consequence, SLE should be considered in the differential diagnosis of all forms of kidney injury.