CIDP (chronic inflammatory demyelinating polyneuropathy) is an autoimmune disease. Your immune system mistakenly attacks the protective coating around your peripheral nerves, called the myelin sheath, causing progressive weakness and numbness that develops over at least two months. It affects an estimated 58,000 people in the United States, with roughly 3.6 new cases per 100,000 people each year.
How the Immune System Attacks Your Nerves
In a healthy body, the myelin sheath works like insulation around a wire, allowing electrical signals to travel quickly along your nerves. In CIDP, the immune system treats this insulation as a threat and launches a coordinated attack against it.
The process starts when certain white blood cells cross the blood-nerve barrier, a protective layer that normally keeps immune cells out of nerve tissue. Once inside, these cells release inflammatory signals that recruit additional immune cells, particularly macrophages. Nerve biopsies from people with CIDP show macrophages physically peeling apart the myelin layers of otherwise healthy nerve cells. As the myelin breaks down, nerve signals slow or fail entirely, producing the weakness and sensory changes that define the disease.
In some patients, the immune system also produces antibodies that target specific proteins at critical junctions along the nerve. These proteins act like glue holding the myelin sheath tightly to the nerve fiber. When antibodies strip them away, the myelin detaches and the underlying nerve fiber can degenerate. About 7% of CIDP patients carry antibodies against one of these junction proteins (called NF155), and roughly 2% carry antibodies against another (CNTN1). These antibody-positive subtypes tend to cause more severe symptoms, often with prominent tremor, and respond differently to treatment than typical CIDP.
How CIDP Differs From Guillain-Barré Syndrome
CIDP is sometimes called the chronic version of Guillain-Barré syndrome (GBS), and the two share the same basic problem: immune-mediated destruction of peripheral nerve myelin. The key difference is timing. GBS is a one-time event that reaches its worst point within four weeks. CIDP, by definition, progresses for more than two months and then follows a relapsing-remitting, steadily progressive, or occasionally single-episode course.
This distinction matters in practice because some people initially diagnosed with GBS turn out to have CIDP. If someone thought to have GBS worsens again after eight weeks, or deteriorates three or more times, clinicians consider reclassifying them as having acute-onset CIDP. In studies comparing the two, all patients who ultimately had CIDP experienced their first worsening after 4.5 weeks, while those with true GBS relapsed within 4 weeks (median of 18 days).
Symptoms and What They Feel Like
CIDP typically begins with symmetrical weakness in both legs, progressing to the arms over weeks to months. You might notice difficulty climbing stairs, trouble gripping objects, or a general sense of heaviness in your limbs. Sensory symptoms are common too: tingling, numbness, or a loss of balance that worsens in the dark or on uneven surfaces.
Unlike conditions that cause sudden, dramatic episodes, CIDP tends to creep in gradually. Some people go months before the symptoms become disruptive enough to seek medical attention. The slow onset is part of what makes it tricky to recognize, since many other conditions can cause similar complaints.
How CIDP Is Diagnosed
There is no single blood test for CIDP. Diagnosis relies on a combination of clinical findings, nerve conduction studies, and sometimes a spinal tap. The most recent international guidelines (updated in 2021 by the European Academy of Neurology and Peripheral Nerve Society) require nerve conduction tests that include sensory nerve studies, with separate criteria for typical CIDP and its recognized variants.
On a spinal tap, the hallmark finding is elevated protein in the cerebrospinal fluid with a normal white blood cell count. Most labs consider anything above 0.45 g/L elevated; people with confirmed CIDP average around 1.0 g/L, more than double the threshold. This pattern of high protein without excess white cells helps distinguish CIDP from infections or other inflammatory conditions that affect the nervous system.
For patients suspected of having an antibody-driven subtype, specialized blood tests can check for antibodies against the junction proteins NF155, CNTN1, and CASPR1. A positive result doesn’t just confirm the diagnosis. It can also predict how well someone will respond to standard treatments and whether alternatives might work better.
Treatment and Long-Term Outlook
The three first-line treatments for CIDP are immunoglobulin infusions (IVIg), corticosteroids, and plasma exchange. All three work by dampening or resetting the immune response, though through different mechanisms. Most people with CIDP respond to at least one of these options, and the choice often depends on individual factors like symptom severity, other health conditions, and how quickly improvement is needed.
Long-term outcomes vary widely. In one study following patients treated with corticosteroids, about one-third achieved cure or lasting remission, meaning they could stop treatment entirely. Another third had stable disease but needed ongoing maintenance therapy to keep symptoms controlled. The remaining patients either didn’t respond adequately or had a more complicated course. Roughly one in four patients responded well to just one or two rounds of steroid treatment.
For the subset of patients with antibodies against junction proteins who don’t respond to standard immunoglobulin therapy, treatments that specifically target the antibody-producing cells can be effective. This approach works by depleting the immune cells responsible for making the harmful antibodies, and case reports have shown meaningful improvement in patients who had already failed conventional treatment.
The overall trajectory for most people with CIDP is manageable but requires ongoing attention. Some people eventually taper off treatment and stay in remission. Others need periodic infusions or medications for years. Early diagnosis and treatment generally lead to better outcomes, since prolonged nerve damage from untreated inflammation can become permanent even after the immune attack is controlled.