PLA2R1 and systemic lupus erythematosus: Approximately 60% of patients with lupus have renal involvement, or LN, and 10% to 20% of these patients have membranous LN (class V), which can be pure or mixed with proliferative lesions of classes III and IV.[8] Membranous LN, a secondary membranous nephropathy, is PLA2R and THSD7A negative.