Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated disorder of peripheral nerves. Intravenous immunoglobulins (IVIg) are a first line therapy for CIDP. The investigators used a transcriptomic approach to compare the gene expression profiles in the peripheral blood of patients having a CIDP or autoimmune diseases, before and after IVIg treatment, in order to identify their mechanism of action in this condition, to lead to a better understanding of CIDP pathophysiology, and potentially determine factors associated with the response to the treatment.