How Does Diabetes Affect Charcot-Marie-Tooth Type 1A?

Having Charcot-Marie-Tooth disease type 1A (CMT1A) means your peripheral nerves are already vulnerable due to a genetic mutation. If you develop diabetes or high blood sugar, it can act as a “second hit” to these delicate nerves ^[1]. High blood sugar causes its own type of nerve damage known as diabetic neuropathy. When diabetic neuropathy occurs on top of the existing damage from CMT1A, it accelerates the loss of nerve fibers, impairs nerve regeneration, and drastically worsens symptoms like muscle weakness and numbness ^[1].

The “Second Hit” to Your Nerves

To understand why your doctor wants you to be extra careful about your blood sugar, it helps to look at how these two conditions affect your nerves differently:

• CMT1A’s Impact: CMT1A primarily affects the myelin sheath—the protective insulation around your nerve fibers (axons) ^[2]. Because the insulation is faulty, nerve signals travel slower, and over time, the underlying nerve fibers can become damaged.
• High Blood Sugar’s Impact: Chronic high blood sugar damages the tiny blood vessels that supply oxygen and nutrients to your nerves. It also causes oxidative stress and metabolic dysfunction (cellular damage and energy problems), directly injuring the nerve fibers themselves ^[3][4].

When you have both conditions, your nerves face a “double hit.” Studies show that patients with CMT1A and co-existing diabetes (or even impaired glucose tolerance, often called prediabetes) experience a severe worsening of both daily symptoms and underlying nerve damage ^[1]. This disrupts how the nerve fiber and its protective coating support each other, leading to an increased loss of nerve fibers ^[1].

How Symptoms Can Change

If high blood sugar begins affecting your nerves alongside CMT1A, the first and most common change is a rapid worsening of your existing distal symptoms (numbness and weakness in your hands and feet). In addition to this, medical research notes that people with both CMT1A and glucose metabolism disorders often develop proximal weakness (weakness in the muscles closer to the center of the body, like the thighs or upper arms), which is less common in typical CMT1A ^[5].

Furthermore, diabetic neuropathy often causes burning pain, tingling, or a “stocking-glove” pattern of numbness in the hands and feet. Because both conditions can lead to reduced sensation in your feet, you are at a much higher risk for developing slow-healing foot sores or plantar ulcers ^[6].

Protecting Your Nerves

While you cannot change the genetic mutation that causes CMT1A, your blood sugar is something you and your medical team can manage.

• Monitor Your Blood Sugar: Regular screenings, such as an HbA1c test (which measures your average blood sugar over three months), are crucial. Catching elevated blood sugar early allows you to intervene before it causes significant nerve damage.
• Comprehensive Management: If you are diagnosed with diabetes, aggressive management of your glucose levels—through medication, diet, and exercise—is considered highly beneficial for preventing further progression of neuropathy and avoiding severe complications ^[6].
• Daily Foot Checks and Podiatry: Because of the compounding numbness from both conditions, inspect your feet daily for any cuts, blisters, or pressure sores. Establishing care with a podiatrist for professional foot care and custom orthotics is a critical preventative step.

By keeping your blood sugar in a healthy range, you are actively protecting your vulnerable nerves from unnecessary additional damage.