Validation of Cutaneous Nerve Demyelination in Diagnosis and Treatment of CIDP

Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) is an autoimmune disorder that can cause severe weakness and numbness, difficulty walking if untreated. CIDP is a disorder where the myelin or outside covering of the nerves which protect nerves and speed conduction are damaged by the immune system. The typical way CIDP is diagnosed is by performing electrical stimulation of the nerves (nerve conduction study or NCS) which may not be very accurate in identifying CIDP. The investigators also are not clear on how CIDP nerve impairment improves with treatment after IVIg, which is the recommended treatment. This study uses skin biopsy of the finger to look at the nerves and see if abnormalities of myelin such as segmental demyelination (loss of myelin along the course of the nerve) can be detected under microscope. The investigators will repeat the skin biopsy during treatment with IVIg (brand Privigen which is FDA approved for CIDP) to determine how IVIg improves nerves during treatment. The investigators hope this study will provide both better ways to diagnose patients with CIDP as well as inform doctors on how CIDP can improve with treatment. The investigators are recruiting patients newly diagnosed or within 6 months of diagnosis to study the use of skin biopsies in diagnosis of CIDP. The investigators are also repeating skin biopsies at 3 months and 6 months to measure improvement in nerve demyelination.