What is the Difference Between CIDP and CMT1A?

The main difference between CIDP (Chronic Inflammatory Demyelinating Polyneuropathy) and CMT1A (Charcot-Marie-Tooth disease type 1A) is their underlying cause. CMT1A is a genetic condition caused by an extra copy of the PMP22 gene, which affects how the protective coating (myelin) on your nerves develops ^[1]. CIDP, on the other hand, is an autoimmune condition where your body’s immune system mistakenly attacks healthy myelin ^[2].

Receiving a new diagnosis after you have already been diagnosed with CIDP can be incredibly frustrating and emotionally exhausting. It is normal to feel overwhelmed when shifting from an autoimmune condition you thought could be treated with immune therapies to a lifelong genetic condition. However, distinguishing between the two is critical. Treatment for CIDP—which involves suppressing the immune system—does not work for CMT1A and can expose you to unnecessary risks ^[3]. While CMT1A cannot be treated with immune therapies, its symptoms can absolutely be managed to help you maintain your independence and quality of life.

Key Differences at a Glance

How Nerve Damage Happens: Uniform vs. Patchy Slowing

When a doctor suspects either of these conditions, they will order Nerve Conduction Studies (NCS) or an Electromyogram (EMG). These tests measure how fast electrical signals travel through your nerves.

• In CMT1A (Uniform Slowing): Because the condition is genetic, every Schwann cell (the cells that make myelin) has the same genetic mutation. As a result, the nerve damage is consistent and evenly distributed throughout your body. Your test results will show uniform slowing—meaning the electrical signals travel slowly at a relatively steady speed across all your nerves ^[4].
• In CIDP (Non-Uniform or Patchy Slowing): Because the immune system attacks the nerves in unpredictable spots, the myelin damage is uneven. Electrical signals might travel at a normal speed in one part of a nerve but slow down drastically or stop completely in another part. This patchy damage creates specific patterns on an EMG, which neurologists refer to as conduction block or temporal dispersion ^[5][4].

Why Misdiagnosis Happens

It is relatively common for doctors to initially suspect CIDP in someone who actually has CMT1A ^[2]. Both diseases cause demyelination (damage to the myelin sheath), which leads to muscle weakness, numbness, and balance issues.

Sometimes, early or less typical cases of CMT1A can show uneven patterns on nerve tests that briefly look like an immune attack ^[6]. Additionally, because CIDP can be treated with immune therapies, doctors often prefer to cautiously trial these treatments if they are uncertain, rather than immediately diagnose a genetic condition that doesn’t respond to those same medications. Knowing this can help explain why your doctor initially started you on treatments like IVIG or steroids—they were trying to be cautious and give you the benefit of a potentially highly effective therapy.

The Importance of Getting It Right

Distinguishing between the two conditions is vital for your long-term health. If you actually have CMT1A, mistakenly treating it as CIDP means you will receive immunosuppressive therapies like IVIG (intravenous immunoglobulin), steroids (like prednisone), or plasma exchange. These treatments cannot repair a genetic defect, meaning they offer no real benefit for CMT1A ^[3]. More importantly, they carry significant side effects, including an increased risk of infections, high blood pressure, and long-term immune system suppression ^[3].

Confirming Your Diagnosis and Next Steps

If your doctor suspects your diagnosis might be changing from CIDP to CMT1A, the only definitive way to confirm CMT1A is through genetic testing ^[1]. A simple blood or saliva test can look for the duplication of the PMP22 gene.

Because CMT1A is a genetic condition, a positive test also means your children and blood relatives might carry the gene. A genetic counselor can help you navigate what this means for your family.

If testing confirms CMT1A, you and your care team will shift your focus to therapies that manage CMT1A, such as physical therapy, specialized bracing (orthotics), and regular monitoring ^[3]. It is crucial that you do not stop taking any current CIDP medications, especially steroids, suddenly on your own. Work directly with your doctor to create a safe, carefully monitored tapering plan to come off these medications gradually.