Spinal muscular atrophy (SMA) is a rare condition and majorly affects the motor neurons in the spinal cord. These neurons are essential components of the central nervous system and are responsible for controlling muscle movement. As a result of this condition, the muscles in various organs undergo atrophy and become weak and degenerate. SMA is classified into the following four main types on the basis of the severity of the condition.

Type 1
Type 1 SMA is sometimes known as Werdnig-Hoffmann disease and is considered to be the most severe of the four types. Out of all the people suffering from SMA, 60% of people are known to be suffering from type 1. In this type, major symptoms are observed within the first six months from the child being born. Such babies may have trouble holding up their heads or even sucking and swallowing. This condition often leads to other conditions such as respiratory infections and pneumothorax due to the weakening of muscles.

Type 2
This type of SMA is also called Dubowitz disease, and it is usually diagnosed in children between six months and 18 months of age. AS opposed to type 1, children with type 2 SMA can better manage this condition and have better chances of living a relatively normal life up to adulthood. This is an intermediate form of atrophy that may sometimes cause difficulty in walking without external support in some children.

Type 3
This form of SMA is milder than type 2, and the symptoms of atrophy are usually not observed before the child is at least 18 months old. Type 3 SMA is also sometimes referred to as Kugelbert-Welander or juvenile-onset SMA, and can it sometimes show no symptoms until the early stages of adulthood. Some patients may face a little trouble while walking and might need to use a wheelchair, but on the whole, people suffering from type 3 SMA are usually expected to have a normal life span.

Type 4
This is the mildest form of SMA observed in people. The symptoms of this type of SMA are not known to appear until a person is in their mid-30s. This form of SMA is quite rare and known to progress quite slowly. Due to the mild symptoms and slow progression of this disease, people with type 4 SMA are known to lead normal, mobile lives without even knowing that they are suffering from this disease.

One must consult a doctor for prompt diagnosis and treatment.