What are the causes of primary Membranous Nephropathy?
M-type phospholipase A2 receptor (PLA2R) on the human podocytes is the target antigen in at least 70% of patients with primary Membranous Nephropathy, and anti-PLA 2 R autoantibodies have been detected in the sera of these patients.
Thrombospondin type-1 domain containing 7A (THSD-7A) is another podocyte antigen that accounts for an additional 10% of patients with primary MN that are negative for anti-PLA 2 R antibody.
As a rule, patients with positive anti-THSD-7A autoantibodies have negative sera for anti-PLA 2 R antibodies, although rare cases of dual positivity have been reported.
Taken together, autoantibodies to these podocyte-specific antigens are the cause of primary Membranous Nephropathy in almost 80% of patients.
Although these findings do not explain the cause in all cases of Membranous Nephropathy, they suggest that additional antibodies against podocyte proteins are likely to be identified.