Anti-contactin 1 Antibody-associated Membranous Nephropathy in Chronic Inflammatory Demyelinating Polyneuropathy with Several Autoantibodies.

A 50-year-old man diagnosed with anti-contactin 1 (CNTN1) antibody-associated chronic inflammatory demyelinating polyneuropathy (CIDP) was referred to our department for the evaluation of proteinuria. A kidney biopsy revealed membranous nephropathy (MN). Immunohistochemistry for CNTN1 revealed positive granular staining along the glomerular basement membrane, confirming anti-CNTN1 antibody-associated MN. Immunofluorescence showed a full-house pattern, and several autoantibodies, such as anti-nuclear antibody, anti-double-strand DNA antibody, and anti-cardiolipin antibody, were detected in the patient's serum. Although limited autoantibodies have been investigated in some of the reported cases, a variety of autoantibodies might be produced in anti-CNTN1 antibody-associated CIDP, accompanied by MN.