CIDP, short for chronic inflammatory demyelinating polyradiculoneuropathy, is a rare autoimmune disorder in which the immune system attacks the protective coating around peripheral nerves. This leads to progressive weakness and numbness, typically in the legs and arms, that develops over at least eight weeks. It affects roughly 7 to 10 people per 100,000 and is three times more common in men than women, with rates climbing sharply after age 50.
How CIDP Damages Your Nerves
Peripheral nerves carry signals between your brain and the rest of your body. Each nerve fiber is wrapped in a fatty insulating layer called myelin, which speeds those signals along, much like the rubber coating on an electrical wire. In CIDP, your immune system mistakenly treats that myelin as a threat.
Several parts of the immune system team up to do the damage. T-cells and macrophages infiltrate the nerves and nerve roots directly. The macrophages physically strip myelin off nerve fibers through a process called phagocytosis. At the same time, antibodies (IgG and IgM) deposit on the surface of the cells that produce myelin and on the myelin itself, flagging them for further immune attack. The complement system, a separate arm of innate immunity, amplifies the destruction. The result is patchy demyelination along peripheral nerves, which slows or blocks the electrical signals that control movement and sensation.
Typical Symptoms
The hallmark of CIDP is symmetric weakness that affects both sides of the body roughly equally. Unlike many neuropathies that start at the fingertips and toes and work inward, CIDP hits proximal muscles (thighs, hips, upper arms) and distal muscles (hands, feet) at the same time. You might notice difficulty climbing stairs, getting out of a chair, or gripping objects, all worsening gradually over months.
Sensory symptoms follow a specific pattern. Vibration sense and position sense (your ability to tell where your limbs are without looking) are affected more than pain and temperature sensation. Many people describe a feeling of unsteadiness or clumsiness before they notice overt numbness. Reflexes at the knee and ankle are typically reduced or absent. About one-third of patients experience a relapsing-remitting course, with periods of worsening followed by partial recovery, while the rest have a slow, steady decline.
How CIDP Differs From Guillain-Barré Syndrome
CIDP is sometimes called the chronic cousin of Guillain-Barré syndrome (GBS), and the two share similar immune mechanisms. The critical difference is timing. GBS reaches its worst point within four weeks and is considered an acute illness. CIDP, by definition, must progress for at least eight weeks before a diagnosis is made. Some patients develop what looks like GBS initially but then continue to worsen or relapse beyond that eight-week mark, at which point the diagnosis shifts to CIDP.
How It Is Diagnosed
There is no single test for CIDP. Diagnosis relies on a combination of clinical findings, nerve conduction studies, and sometimes a spinal fluid analysis. Nerve conduction studies look for specific patterns of slowed conduction velocity and conduction block, both signs that myelin is damaged rather than the nerve fibers themselves.
A spinal tap can provide supporting evidence. About 90% of people with CIDP have elevated protein levels in their cerebrospinal fluid (above 45 mg/dL) while white blood cell counts remain normal, a pattern called cytoalbuminologic dissociation. If the white cell count exceeds 10 cells per cubic millimeter, doctors typically look for other causes such as infection. Symptoms must be present for at least eight weeks and affect at least two limbs before CIDP is formally diagnosed.
Treatment Options
Three first-line treatments exist for CIDP: immunoglobulin therapy, corticosteroids, and plasma exchange. The choice depends on symptom severity, patient preference, and how quickly improvement is needed.
Immunoglobulin Therapy
Intravenous immunoglobulin (IVIG) is the most studied treatment. In clinical trials, roughly 70 to 78% of patients showed meaningful improvement in disability scores. The median time to a first noticeable response was about four weeks, though patients who had responded to IVIG before often improved within three weeks. Treatment starts with a loading dose given over several days, followed by maintenance infusions every three weeks.
For long-term maintenance, subcutaneous immunoglobulin (SCIG) is an alternative that patients can self-administer at home. It delivers more consistent levels of immunoglobulin between doses and is associated with improved quality of life compared to repeated IV infusions. Weekly dosing is typical, and many patients transition from IVIG to SCIG at a comparable dose once they are stable.
Corticosteroids
Steroids suppress the overactive immune response more broadly. A common starting regimen uses a moderate to high daily dose, with noticeable improvement sometimes appearing within two weeks, though full benefit may take six months. The medication is then tapered slowly over months to find the lowest effective dose. Tapering too quickly raises the risk of relapse. Response rates for steroids are around 40%, lower than IVIG, but steroids cost far less and can be taken orally.
Plasma Exchange
Plasma exchange filters harmful antibodies directly from the blood. It works quickly but requires repeated sessions, usually at a medical center. It is most often used as a bridge while waiting for other treatments to take effect or when IVIG and steroids have not been sufficient.
Long-Term Outlook
CIDP is a chronic condition, but outcomes vary widely. A five-year follow-up study of 38 patients found that 26% achieved complete remission lasting more than two years with normal nerve conduction results. Another 61% reached partial remission and were still able to walk, though about half of that group continued on some form of immune therapy. Overall, 39% of patients were still receiving treatment five years after their initial diagnosis.
The people most likely to need ongoing therapy are those with a relapsing-remitting course or those who responded only partially to initial treatment. Age at onset, the severity of nerve damage at diagnosis, and how quickly treatment begins all influence long-term outcomes. Early diagnosis matters because prolonged demyelination can eventually cause permanent damage to the underlying nerve fibers themselves, which is much harder for the body to repair than myelin loss alone.
Who Is Most at Risk
CIDP can occur at any age, but the risk increases dramatically with time. In a large Dutch epidemiological study, the incidence rate in people under 50 was just 0.09 per 100,000 person-years. In those 50 and older, it jumped to 1.50 per 100,000, roughly a 17-fold increase. Prevalence followed the same pattern: about 3.3 per 100,000 in younger adults compared to 20.5 per 100,000 in those over 50. No specific genetic markers or environmental triggers have been definitively identified, though the condition occasionally follows a viral infection or vaccination.