Patient description: A 40-year-old woman with no past medical history presents to the ER with excruciating pain in her right arm that had started 1 hour prior to her admission. She denies trauma. On examination she is pale and in moderate discomfort, as well as tachypneic and tachycardic. Her body temperature is normal and her blood pressure is 80/60. Her right arm has no discoloration or movement limitation.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Chronic Inflammatory Demyelinating Polyneuropathy IVIG-untreated subjects Either subjects with newly diagnosed CIDP (developing over at least 2 months) or subjects with an IVIG treatment interruption for at least 1 year with a progressive disease (deteriorating in the last 2 months) prior to enrolment Actual diagnosis (including electrophysiology) of CIDP with progressive or relapsing dysfunction from motor and sensory or symmetric motor nerve only in at least 1 limb resulting from neuropathy. for definite or probable CIDP according to EFNS/PNS guideline Age ≥18 years Male or female Written informed consent for study participation obtained before undergoing any study specific procedures IVIG-pretreated subjects Being treated regularly with IVIG on a fixed cycle length of 2 to 6 weeks ± 5 days in the last 6 months, on a fixed dosage of ± 20 % in the last 6 months and deteriorating by at least 1 INCAT score point during the Washout Period of up to 10 weeks (except for an increase from 0 to 1 solely due to upper limb score) Historic diagnosis of CIDP with progressive or relapsing dysfunction from motor and sensory or symmetric motor nerve only in at least 1 limb resulting from neuropathy. for definite or probable CIDP according to EFNS/PNS guideline Age ≥18 years  A motor syndrome that fulfils for multifocal motor neuropathy (MMN) with conduction block (i.e., upper limb motor weakness without sensory deficit and with a 50% decrease in action potential amplitude or area on proximal compared with distal stimulation in motor nerves) CIDP with monoclonal gammopathy of uncertain significance (CIDP-MGUS) with anti-MGUS antibodies and patients with distal acquired demyelinating symmetric (DADS)neuropathy Any disease (mainly neurological or chronic orthopedic) that may cause symptoms or may interfere with treatment or outcome assessments with the INCAT (e.g., diphtheria, drug or toxin exposure and diabetes mellitus likely to have caused the neuropathy, IgM paraproteinemia, familial neuropathy, borreliosis with radiculopathy, post-polio-syndrome,M. Parkinson, stroke) Current malignancy History of cardiac insufficiency (New York Heart Association [NYHA] III/IV), cardiomyopathy, significant cardiac dysrhythmia requiring treatment, unstable or advanced ischemic heart disease, congestive heart failure or severe hypertension History of thrombotic episodes (deep vein thrombosis, myocardial infarction, cerebrovascular accident) Migraine associated with IVIG infusion in the last 3 months prior to enrolment Known allergic or other severe reactions to blood products including intolerability to previous IVIG (i.e. severe headache, hypersensitivity, intravascular hemolysis) Subjects with serum IgA level less than 50% of the lower normal limit Known hyperprolinemia