Symptoms of AFM

  • AFM is a rare but serious neurologic condition. Sudden onset of arm or leg weakness, loss of muscle tone, and loss of reflexes are the most common symptoms.
  • Seek medical care right away if you or your child develops any of these symptoms.

Most people will have sudden onset of:

  • Arm or leg weakness
  • Loss of muscle tone and reflexes
AFM symptoms: sudden arm or leg weakness


Some people will also have:

  • Facial droop or weakness
  • Difficulty moving eyes
  • Drooping eyelids
  • Difficulty swallowing
  • Slurred speech
  • Pain in arms or legs
  • Pain in neck or back
AFM symptoms: difficulty moving the eyes or drooping eyelids

Difficulty moving the eyes or drooping eyelids

AFM symptoms: facial droop or weakness

Facial droop or weakness

AFM symptoms: difficulty with swallowing or slurred speech

Difficulty with swallowing or slurred speech


In rare cases, people may also:

  • Have numbness or tingling
  • Be unable to pass urine (pee)

The most severe symptoms of AFM are:

  • Respiratory failure: This happens when the muscles involved with breathing become weak and can require a ventilator (a machine to help them breathe).
  • Serious neurologic complications such as body temperature changes and blood pressure instability that could be life threatening.
Seek Medical Care Right Away
  • If you or your child develops any of these symptoms, you should seek medical care right away.
  • Clinicians should immediately admit patients to the hospital since AFM can progress rapidly and require urgent medical intervention, like assistance with breathing.
  • Your clinicians should collect information about your symptoms and send this information to their state or local health departments.
Page last reviewed: February 25, 2020