Spinal Muscular Atrophy and Poor Muscle Tone

SMA is characterized by a progressive loss of muscle control, muscle movement, and increasing muscle weakness. Most people with SMA start showing the first symptoms early in life (as early as birth) and the disease becomes more severe over time.

Because it is a muscle-related disease, the proximal muscles (closer to the center of the body) are more severely affected than the most distant muscles, such as those in the hands and feet.

People with SMA may never acquire or may gradually lose the ability to walk, sit, or move. In addition, normal growth and development can also place additional stress on muscles that are already weakened.

SMA does not impact intelligence.

Spinal muscular atrophy and poor muscle tone

Babies with SMA type 1 have thin and weak muscles, making their limbs limp and floppy. Usually they are unable to raise their head or sit without support, achieve little or no movement, and experience muscle weakness that gets worse with time.

People with SMA type 2 may show a slight tremor in their fingers. Posture becomes worse over time as muscles shrink and deformation of the hands, feet, chest and joints occur.

People with SMA type 3 may experience balance problems and/or difficulty with walking, running, or climbing stairs. They may show a slight tremor of their fingers. All are results of poor muscle tone.

For people with SMA type 4, the symptoms are usually mild to moderate and may include muscle weakness in the hands and feet, difficulty walking, muscle tremor, and twitching.

Read the latest news about muscle wasting in spinal muscular atrophy at SMA News Today.

Follow the latest developments for all experimental Spinal Muscular Atrophy treatments on the SMA Therapy Tracker.

SMA News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.


  1. https://www.smafoundation.org/about-sma/faq/
  2. https://medlineplus.gov/ency/article/000996.htm