Neural Epidermal Growth Factor–Like 1 Protein–Positive Membranous Nephropathy in Chinese Patients

Background and objectives The neural EGF-like 1 (NELL-1) protein is a novel antigen in primary membranous nephropathy. The prevalence and clinical characteristics of NELL-1–positive membranous nephropathy in Chinese individuals with primary membranous nephropathy are unclear. Design, setting, participants, & measurements A total of 832 consecutive patients with biopsy-proven primary membranous nephropathy were enrolled. The glomerular expression of phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A) was screened. Glomerular immunohistochemistry staining for NELL-1 was performed in 43 patients with PLA2R- and THSD7A-negative membranous nephropathy, 31 patients with PLA2R-positive membranous nephropathy, and two patients with PLA2R and THSD7A double positivity. The NELL-1 antibody was also detected in the sera of patients with NELL-1–positive membranous nephropathy by western blot. Clinical and pathologic features were comparable between patients with isolated NELL-1–positive, isolated PLA2R/THSD7A-positive, and triple antigen–negative membranous nephropathy. Results Among the 832 patients with primary membranous nephropathy, 11 of 54 (20%) patients with PLA2R-negative membranous nephropathy had THSD7A-positive membranous nephropathy. NELL-1–positive membranous nephropathy accounted for 35% (15 of 43) of all patients with PLA2R- and THSD7A-negative membranous nephropathy. One patient was double positive for NELL-1 and PLA2R in glomerular deposits and positive for only the PLA2R antibody in the serum. Most patients with NELL-1–positive membranous nephropathy were women. No tumors were found. There were significant differences in the prevalence of IgG subtypes between patients with different antigen positivity. Among patients with isolated NELL-1–positive membranous nephropathy, although 80% (12 of 15) were IgG4 staining positive, the proportion of IgG4 dominance was only 67% (ten of 15). Conclusions About one third of patients who were PLA2R and THSD7A negative were NELL-1 positive in Chinese patients with primary membranous nephropathy. NELL-1–positive membranous nephropathy was more common than THSD7A-positive membranous nephropathy in PLA2R-negative membranous nephropathy.