Spinal muscle atrophy (SMA) is a genetic health condition that affects a particular section of the nervous system, which controls voluntary muscle movement. Most of the nerve cells that control muscles are placed in the spinal cord, which accounts for the term “spinal” in this disease. The word “muscle” is used because the disease has a primary impact on muscles, which do not get any signal from the nerve cells. When muscles are inactive, they become smaller; “atrophy” is the medical term used for this condition. SMA is a common genetic condition that affects children and infants. It is very rarely found in adults. According to estimates, one out of every 6,000 to 10,000 babies across the globe is born with SMA.

Now that you have got a basic understanding of what is SMA, explained herein are some of the important spinal muscle atrophy (SMA) types that you should have knowledge about.

1. Type 1 SMA
Type 1 SMA is the most common and severe type. Also known as Werdnig-Hoffman Disease, this type of SMA is usually detected at birth or after the first few months, which could be any time before the baby is six months old. The symptoms of this SMA type include weak trunk movement and floppy limbs. Children with this type of SMA are quite immobile and have restricted the ability to move. They have to face difficulty in breathing, holding their head up, swallowing, and feeding. Infants born with this SMA type are unable to sit. This type of SMA progresses quickly with the muscles getting weaker, which leads to a regular respiratory infection. Type 1 SMA can lead to the death of the baby by the age of two.

2. Type 2 SMA
Type 2 SMA is also known as intermediate SMA. With this type, symptoms usually occur at any time between the ages of 7 to 18 months. In this type, the progression rate can vary to a great extent. Children with the problem of Type 2 SMA are unable to stand and have respiratory infections. In the type of SMA, life expectancy can range from early childhood to adulthood, depending on how severe the patient’s condition is.

3. Type 3 SMA
Type 3 SMA is of a mild form that is also known as Juvenile Spinal Muscular Atrophy or Kugelberg-Welander Muscular Atrophy. Symptoms this type of SMA can occur from the age of eighteen months to their early adulthood. Patients with this type are able to walk and stand but have difficulty in getting up from sitting position. They are at a higher risk of getting respiratory infections and may also experience mild weakness. The life expectancy in this type is close to normal.

4. Type 4 SMA
Type 4 SMA is seen in adults. It is a rare type wherein the disease does not occur before the second or third decade of life. Patients with this type are able to walk during adulthood. However, they gradually experience muscle weakness and other typical symptoms. If you notice any of these symptoms in yourself or your kid, you must visit the doctor immediately.