Since 1973, a few cases of concomitant inflammatory demyelinating polyradiculoneuropathy and nephrotic syndrome have been reported. The neuropathy was either an acute inflammatory demyelinating polyneuropathy (AIDP) or a chronic inflammatory demyelinating polyneuropathy (CIDP), and the nephrotic syndrome was related to either a focal segmental glomerulosclerosis (FSGS) or a membranous glomerulonephritis (MGN). Time course, severity, and response to treatment were heterogeneous, and evolution of neuropathy and nephropathy could be independent. This suggests that common epitopes are targeted by autoantibodies within the peripheral nerve and the glomerular filtration barrier. However, the antigenic targets are unknown. Here, we report a patient who developed CIDP associated with anti-contactin-1 immunoglobulin G4 (IgG4) antibodies and nephrotic syndrome.