What Is Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)?
CIDP is a rare autoimmune neurological disorder that affects the peripheral nervous system (PNS). In CIDP, the body’s own immune system mistakenly attacks its peripheral nerves, leading to damage and loss of the myelin sheath that surrounds the nerves. This demyelination disrupts normal nerve signaling and results in the symptoms associated with CIDP.
What Is Myelin?
The myelin sheath is a membranous insulating layer that surrounds nerve fibers (Figure 1). Its primary function is to accelerate the transmission of electrical signals along the nerves, allowing for efficient communication within the nervous system.
Figure 1. Myelin Sheath
Why Does the Immune System Attack Our Own Nerves?
The primary role of the immune system is to recognize and eliminate viruses, bacteria, and tumor cells—precisely targeting what is “non-self” while maintaining immune tolerance toward the body’s own tissues. The immune system distinguishes between self and non-self by recognizing molecules known as antigens.
In CIDP, however, this recognition process malfunctions. The immune system mistakenly identifies the body’s own nerve cells as foreign and launches an immune attack against them.
The autoimmune response in CIDP mainly involves T cells, macrophages, and B cells. Acting together, these immune cells attack the myelin sheath of peripheral nerves, leading to demyelination (Figure 2). Once the myelin sheath is damaged, nerve signal transmission slows down or may even be blocked entirely, resulting in symptoms such as muscle weakness, numbness, abnormal sensations, and difficulty walking.
Why the immune system incorrectly identifies nerve cells as enemies remains an active area of medical research. Current understanding suggests that multiple factors contribute to this process. One widely accepted explanation is known as molecular mimicry. Certain viruses or bacteria share structural similarities with components of the myelin sheath. As a result, when immune cells attack these pathogens, they may inadvertently also attack myelin that resembles the “invaders.”
In addition to molecular mimicry, other contributing factors may include genetic or innate susceptibility, meaning that some individuals are born with immune systems that are more prone to autoimmune errors.
Figure 2. Demyelination
Why Is CIDP a Chronic Condition?
CIDP is considered chronic because it results from a persistent autoimmune attack on the myelin sheath of peripheral nerves, rather than a short-term immune response. The immune system continuously damages and strips away myelin over an extended period, leading to long-lasting symptoms. This chronicity is partly due to immune memory, in which the immune system mistakenly continues to recognize nerve components as targets of attack.
Another related disorder is Guillain–Barré syndrome (GBS), which is also caused by an immune-mediated attack on the myelin of the peripheral nervous system. However, unlike CIDP, GBS typically involves an acute, short-term immune response rather than a prolonged one. A key distinction between CIDP and GBS is duration: in CIDP, immune-mediated nerve damage persists for more than eight weeks.
What Symptoms Does CIDP Cause?
CIDP commonly presents with progressive muscle weakness and a reduction in muscle mass in affected areas, a process known as muscle atrophy. Patients may experience tingling, pins-and-needles sensations, or numbness in the fingers and toes, referred to as paresthesia. Balance and coordination are often impaired, leading to clumsiness and difficulty with movement, and overall mobility may gradually decline. Deep tendon reflexes are frequently reduced or absent, and neuropathic pain may also occur.
In some cases, CIDP can affect additional neurological functions, resulting in difficulty swallowing, weakness of muscles above the neck, double vision, and tremors.