Spinal muscle atrophy is a genetic disorder that results in the loss of muscle movement control. In the country alone, one in every 6,000-10,000 people develops this disease. This genetic disorder affects muscle movements and cannot be cured. It can be caused due to the loss of motor neurons which are specialized nerve cells in the spinal cord as well as in the part of the brain connected to the spinal cord. The loss of motor neurons causes weakness in the patient and muscle atrophy. So, muscles used for activities like crawling, sitting, walking and controlling head movements fail to carry out their functions.
Spinal muscle atrophy linked to chromosome 5
Types 1-4
While symptoms may vary from severe to mild, this variance is based on just how much Survival of Motor Neuron (SMN) or chromosome 5 protein is present in the motor neurons. So, the more the SMN protein there is,
- the later symptoms begin and
- the milder the disease is.
Spinal muscle atrophy not linked to chromosome 5
Some forms of spinal muscle atrophy are not linked with SMN deficiency. These forms vary in terms of severity and which muscles it affects more. Most forms target the proximal muscles or the distal muscles.
Types of spinal muscle atrophy:
- Type O
This is the most severe form of the condition. It can be seen in the later stages of pregnancy where the fetus is found to be less active than what is generally expected. After birth, the baby will display little movement and may be unable to swallow or breathe independently. Death generally occurs for such infants before the age of 6 months. - Type 1
Also known as Werdnig-Hoffman Disease, Type 1 is also classified in the severe category. Infants who have type 1 spinal muscle atrophy face trouble swallowing and breathing which may lead to choking and gagging. The muscle tone of those children is poor and weak. They can’t sit up without a form of support or exercise their motor skills to achieve age milestones. Their intellect is normal in their age bracket. They generally die before the age of two. - Type 2
Also known as Dubowitz Disease, infants between the ages of 6-12 months are affected. Muscle weakness becomes apparent but they can sit up without support. They may lose this ability by the time they reach their mid-teens. They are unable to walk without assistance and have poor muscle strength and tone. Their intelligence level ranges from normal to above average. - Type 3
This can be classified as a milder form of spinal muscle atrophy. It is also known as the Kugelberg-Welander Disease. Occurs in children between 1 year of age and adulthood. Young children may fall frequently and have trouble walking down staircases. The legs are more severely affected than the arms. They can generally stand and walk without any form of assistance. However, there is a chance that they will lose this ability later in life. - Type 4
It is the mildest form of spinal muscle atrophy. Mild to moderate muscle weakness doesn’t set in till a person is in his 20s, 30s, or even later. The affected person can still walk and move without support. There is an abnormal curvature of the spine and there are stiff joints. Mild to moderate twitching or tremors may be experienced by these patients. The affected people generally go on to live their whole lifespan. There can be difficulties in gaining weight and sleeping. Suffering from pneumonia will be common.
Genetic testing can truly help in diagnosing the severity of the disease, and treatments can help the patient lead a better life.
