Common Types of Spinal Muscle Atrophy

Spinal muscular atrophy (SMA) is a group of neuromuscular disorders that result in the loss of motor neurons. This condition causes progressive muscle wasting and weakness. There are different types of spinal muscle atrophy (SMA), each with their own set of signs and symptoms. SMA is a recessive genetic disorder. As a result, a child will only be prone to this condition if both parents carry the affected genes.

The gene affected is the “survival of motor neuron” gene (SMN1 and SMN2). In a majority of the SMA cases, both strains of the SMN1 gene are missing. One has a chance of developing this disease if someone in the family has the condition as well.

The symptoms of spinal muscular atrophy (SMA) vary according to the types. This disease mainly develops in one’s early childhood. However, both adults and children can develop this disease and exhibit the following symptoms:

  • Muscle weakness and decreased muscle tone
  • Limited mobility
  • Delayed gross and fine motor skills
  • Breathing and respiratory problems
  • Difficulty in eating and swallowing
  • Scoliosis (curvature of the spine)
  • Spontaneous and uncontrolled tongue movements

There are mainly four types of spinal muscle atrophy (SMA). They are:

1. Type 1 SMA
This is also known as Werdnig-Hoffmann disease and is the most severe type of SMA. It is evident after birth or in the first few months after birth. The symptoms of this condition are weak trunk movements and droopy limbs. Moreover, children have limited ability to move in this condition. Eating and swallowing among other activities are difficult for these children to perform.

2. Type 2 SMA
The symptoms of this condition start to develop between 7-18 months of age. This disease affects the lower limbs more than the upper limbs. Children lose their ability to stand and develop severe respiratory problems.

3. Type 3 SMA
This kind of SMA is known as juvenile spinal muscular atrophy or Kugelberg-Welander. The signs and symptoms of this condition begin from 18 months and go on until early adulthood. People with this condition may walk and move around but have difficulty sitting up after lying down. They also have weakness in the muscular tissue and respiratory infections.

4. Type 4 SMA
The symptoms of this rare condition usually do not emerge initially. The signs are visible only after the second or third phase. Initially, the affected people can walk but as the condition progresses, they lose the ability to move.

If you notice the signs and symptoms of this disorder, immediately refer to a doctor for early diagnosis and treatment. The symptoms of the condition can be managed if cured.