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Prevalence is about 1/200,000 children and 1-7/100,000 adults, but it is generally accepted that the frequency is underestimated.

Onset may occur at any age but is more common in the 5th and 6th decades. Main clinical manifestations include progressive symmetrical weakness in both proximal and distal muscles of lower and/or upper limbs with partial or complete recovery between recurrences, associated with impaired sensation and absent/diminished tendon reflexes. Disease course is relapsing in 30% of cases, chronic and progressive in 60%, and monophasic with full generally permanent recovery in 10%. In 5-30% of cases, cranial nerve dysfunction may occur. Neuropathic pain, respiratory muscle and sub-clinical CNS involvement have been reported. Autonomic system dysfunction can occur. Children have a more rapid onset, greater disability at the peak and a more frequent relapsing course. CIDP may be associated with hepatitis C, inflammatory bowel disease, lymphoma, HIV, organ transplant, melanoma, or connective tissue disorders.

CIDP could be due to an immune reaction, resulting in segmental and multifocal demyelination that may induce axonal loss with time.

To be diagnosed with CIDP, patients have to present a 2 month history of progression of demyelinating neuropathy (DN), some have a history of infection. CIDP may also appear more than 8 weeks after Guillain-Barré syndrome (GBS, so-called ``acute CIDP''; see this term). Diagnosis is based primarily on clinical and electrophysiological findings. The need for CSF examination and nerve biopsy depends on the level of clinical diagnostic certainty. When manifestations are present for at least 2 months, electroneuromyogram (ENMG) confirms the diagnosis if 3 of the following criteria are present on several nerves: partial motor-nerve (M-N) conduction blocks, reduced M-N conduction velocity, prolonged distal M-N and F-wave latencies. MRI may demonstrate gadolinium enhancement and proximal nerve/root enlargement. Elevated CSF proteins, with no cells, and demyelination/remyelination, often with inflammation, in nerve-biopsy specimens can provide additional supportive data. Biopsy is currently only recommended in cases of clinical suspicion of CIDP in which ENMG is not conclusive. CIDP should be suspected in virtually any multifocal or generalized neuropathy of unknown cause.

Differential diagnoses include chronic acquired polyneuropathies (monoclonal gammopathies, diabetes, toxic neuropathies) or inherited neuropathies (Charcot-Marie-Tooth disease or transthyretin amyloid neuropathy; see these terms).

The decision to treat depends on initial disease severity, age, general health status and potential contraindications to the 3 validated treatments: steroids, intravenous immunoglobulins (IVIg) or plasma exchanges. Patients with pure motor CIDP should be treated with IVIg rather than steroids. In milder forms, clinical observation and possibly steroid therapy (depending on ENMG results) are advised. Plasmapheresis or a combination of steroids and IVIg can be started if none of these treatments are effective. Refractory cases can be treated with intensive immunosuppression. The effect of interferon beta-1a and alpha, etanercept or rituximab remains uncertain. Neuropathic pain can be treated with antiepileptic medications or tricyclic antidepressants.

Quadriplegia, respiratory failure and death can occur but are rare. Patients may present residual symptoms that can lead to reduced quality of life. However long-term prognosis is usually good.