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What is Multifocal Motor Neuropathy (MMN)?

MMN is a rare disease that happens when nerves that control muscles are attacked by the immune system. It usually starts out as muscle weakness in one hand or foot.

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This is MMN

It may feel like there's a lot to learn when it comes to understanding . Before diving into the details about this rare disorder, here are some key points to keep in mind:

About 3,000 to 6,000 people in the US are thought to have MMN

  • MMN is a condition that shows symptoms in adulthood (but may start sooner).
  • It affects one side of the body more than the other, which means it's .
  • Symptoms often start out as weakness, cramping, and/or twitching in one hand or foot (in areas of the body).

Symptoms usually appear around the age of 40

  • Motor without sensory: nerves that control muscles, called , are affected by MMN. It usually does not affect , though.
  • It can be hard to diagnose and often gets misdiagnosed.
  • MMN is not life-threatening. And treatment can help slow its progression.

Learning more about MMN and its symptoms can help you prepare to talk to your doctor.

A man zipping his jacket depicts how difficult it can be if you have MMN.

It can be difficult to zip up a jacket or coat if you have MMN.

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a fast fact about MMN

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What causes MMN

MMN happens when your body's immune system mistakenly attacks part of your nervous system. Because it affects your nerves, MMN is considered a neurological condition.

There are several studies underway, and research is being done to learn more about this rare disease, including the root cause of MMN.

Is MMN genetic?

MMN does not appear to run in families. And there are not any specific genes that seem to be linked to MMN. So if you have MMN, that doesn't mean your children will be more likely to get it.

MMN involves "motor without sensory" neurons

In people with MMN, the immune system interferes with nerves that control your muscles, causing muscle weakness. These types of nerve cells are called motor neurons.

Although MMN affects your muscles, it usually does not cause numbness, tingling, or pain. That's because the type of nerves that make you aware of pressure, heat, cold, or pain—sensory neurons—are usually not affected by MMN.

What happens in the body with MMN?

MMN symptoms usually start out as muscle weakness in one hand or foot. As the disease progresses, its symptoms may spread to other extremities.

In MMN, symptoms occur when the immune system damages the coating of the neuron. When this happens, the nerve is no longer able to transfer signals to muscles. This is called a .

Tap on the dots to learn more about what MMN looks like in the body of someone experiencing muscle weakness in their hand.

A body skeleton graphic depicts what happens in the body with MMN.



If you think you might have MMN, learning more about the diagnostic process can help you and your doctor connect the dots sooner.