We evaluated skin biopsies from 3 patients with anti-Nfasc155 IgG4 antibodies, 1 patient with anti-CNTN1 IgG3/IgG4 antibodies, 1 patient with anti-Caspr1 IgG4 antibodies, 1 patient with anti-Nfasc155 antibodies of an undetectable isotype, and 6 seronegative patients with CIDP. The gene discussed is IGHG3; the disease is chronic inflammatory demyelinating polyradiculoneuropathy.