Pauci-immune Lupus Nephritis in Antiphospholipid Disease: A Diagnostic Challenge

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that leads to immune complex deposition in different organs, especially the kidneys. Pauci-immune lupus nephritis (LN) is a very rare condition. About 40% of SLE cases have a positive antiphospholipid antibody (aPL). So, diagnosing primary antiphospholipid syndrome (APS) in SLE patients is challenging because most symptoms of primary APS can be similar to SLE as described in the American College of Rheumatology/Systemic Lupus Erythematosus International Collaborating Clinics classification criteria for SLE. APS might present as thrombotic microangiopathy (TMA) involving arterioles and glomerular capillaries. We need an adequate renal biopsy to differentiate between lupus and APS nephropathy. A 38-year-old man was diagnosed with biopsy-proven primary APS and LN. Hewas commenced on anticoagulants, pulse steroids, rituximab, and with mycophenolatemofetil as a maintenance therapy in collaboration with the rheumatologist. Here we discuss the occurrence and implications of primary APS and Pauci-immune LN in adults.