Membranous Nephropathy Preceding Systemic Sclerosis: An Unusual Presentation of Systemic Sclerosis sine Scleroderma.

Background. Membranous nephropathy (MN) is generally primary, but it can also occur as a secondary form in association with infections, neoplasms or autoimmune diseases. Systemic Sclerosis (SSc), especially in its sine scleroderma forms or in its early stages, rarely manifests itself as MN. Case report. A 60-year-old woman with onset of nephrotic syndrome and histological picture of MN, in the absence of systemic manifestations. The patient subsequently developed episodes of acute renal failure, recurrent proteinuria and clinical-serological signs suggestive of autoimmune connective tissue disease, including increasing ANA titre with anticentromere pattern and onset of Raynaud's phenomenon. The second renal biopsy showed an evolving picture with extensive interstitial fibrosis and severe arteriosclerosis, consistent with a secondary form of MN. The patient was treated with the Ponticelli regimen and subsequently with rituximab, achieving significant clinical remission. In light of the capillaroscopy and autoantibody profile, a diagnosis of very early systemic SSc (sine scleroderma) was made. Discussion. This case highlights how MN can represent an early and atypical manifestation of SSc sine scleroderma, preceding systemic manifestations by years. The negative anti-PLA2R test, the presence of antinuclear autoantibodies and rapid histological progression pointed towards a secondary autoimmune aetiology. Repeated renal biopsy and immunological monitoring proved to be key tools for diagnosis and therapeutic management. Conclusion. MN secondary to SSc sine scleroderma is a rare but important condition that requires attention and a multidisciplinary approach. Early classification as a secondary form allows for targeted therapy and potentially prevents progression to end-stage renal failure.