Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes called chronic relapsing polyneuropathy (CRP) or chronic inflammatory demyelinating polyradiculoneuropathy (because it involves the nerve roots). CIDP is closely related to Guillain–Barré syndrome and it is considered the chronic counterpart of that acute disease. Its symptoms are also similar to progressive inflammatory neuropathy. It is one of several types of neuropathy.

In its traditional manifestation, chronic inflammatory demyelinating polyneuropathy is characterized by symmetric, progressive limb weakness and sensory loss, which typically starts in the legs. Patients report having trouble getting out of a chair, walking, climbing stairs, and falling. Problems with gripping objects, tying shoe laces, and using utensils can all be brought on by upper limb involvement. Proximal limb weakness is a fundamental clinical characteristic that sets apart chronic inflammatory demyelinating polyneuropathy from the vast majority of distal polyneuropathies, which are far more common. Proprioception impairment, distal paresthesias, loss of feeling, and poor balance are all brought on by sensory involvement. Only a small percentage of cases involve neuropathic pain.

Fatigue has been identified as common in CIDP patients, but it is unclear how much this is due to primary (due to the disease action on the body) or secondary effects (impacts on the whole person of being ill with CIDP).

Numerous reports have outlined a range of clinical patterns that are thought to be chronic inflammatory demyelinating polyneuropathy variations. Different variations include ataxic, pure motor, and pure sensory patterns; additionally, there are multifocal patterns in which the distributions of specific nerve territories experience weakness and sensory loss.

Chronic inflammatory demyelinating polyneuropathy (or polyradiculoneuropathy) is considered an autoimmune disorder destroying myelin, the protective covering of the nerves. Typical early symptoms are "tingling" (sort of electrified vibration or paresthesia) or numbness in the extremities, frequent (night) leg cramps, loss of reflexes (in knees), muscle fasciculations, "vibration" feelings, loss of balance, general muscle cramping and nerve pain. CIDP is extremely rare but under-recognized and under-treated due to its heterogeneous presentation (both clinical and electrophysiological) and the limitations of clinical, serologic, and electrophysiologic diagnostic criteria. Despite these limitations, early diagnosis and treatment is favoured in preventing irreversible axonal loss and improving functional recovery.

There is a lack of awareness and treatment of CIDP. Although there are stringent research criteria for selecting patients for clinical trials, there are no generally agreed-upon clinical diagnostic criteria for CIDP due to its different presentations in symptoms and objective data. Application of the present research criteria to routine clinical practice often misses the diagnosis in a majority of patients, and patients are often left untreated despite progression of their disease.

HIV infection is a factor in the occurrence of CIDP. At every stage of HIV infection, distinct patterns of CIDP, whether progressive or relapsing, have been noted. Increased protein content is linked to CSF pleocytosis in the majority of HIV-CIDP cases. Pregnancy has been linked to a significantly greater risk of relapse.

In one study, 32% of 92 CIDP patients had a history of infection within 6 weeks of the onset of neurological symptoms, with the majority of these infections being non-specific upper respiratory tract or gastrointestinal infections. A different study showed that out of 100 patients, 16% had an infectious event six weeks or less prior to the onset of neurological symptoms: seven patients had CIDP that was related to or followed viral hepatitis, and six had a chronic infection with the hepatitis B virus. The other nine patients had vague symptoms similar to the flu.