Spinal Muscular Atrophy (SMA) is a genetic condition, and one in every 6000-10,000 people are affected by it globally. The impact of the disease is severe, as it hampers an individual’s control over their muscle movements. Though everyone who has SMA undergoes a faulty gene mutation, the resulting symptoms, onset, and progress vary. This is the reason why there are different types of spinal muscular atrophy.
- Type 1
It is the most prominent and severe SMA type and is known as the Werdnig-Hoffmann Disease or the infantile-onset. 60% of all SMA cases are of this type. Kids who have Type-1 SMA show symptoms anytime from after birth until six months. In most cases, signs are visible at three months. A baby with Type-1 SMA cannot hold its head without assistance, has floppy arms and legs, and experience trouble swallowing. Type-1 SMA progresses aggressively, making a child vulnerable to respiratory infections, causing difficulty in breathing. Children diagnosed with Type-1 SMA have a life expectancy of two years.
- Type 2
In this type of spinal muscular atrophy, symptoms show between the age of 6-18 months. Children with Type-2 SMA may be able to sit but not stand or walk. The initial symptoms of Type-2 SMA or Dubowitz disease are weak control of motor movements. If left untreated, the child might lose its ability to sit. In Type-2 SMA, the life expectancy of a child depends on its ability to breathe, as respiratory infections are common. Type-2 SMA primarily impacts the legs and, at times, the arms. Children with Type-2 SMA live until adolescence or young adulthood.
- Type 3
In Type-3 SMA, symptoms appear in the age range of 18 months to teenage years. Children who have Type-3 SMA (Kugelberg-Welander syndrome) can stand and walk independently. However, they may fall often and experience difficulty standing or climbing stairs. A child with Type-3 SMA might experience contractures or scoliosis and shortening of the tendons and muscles, leading to muscle weakness in both legs and arms. They are prone to respiratory infections. Type-3 SMA is the mildest SMA in children and allows a normal life-span.
- Type 4
Type-4 SMA, also known as adult SMA, is rare. Its symptoms do not start till the person is in their 20s or 30s. An adult with Type-4 SMA might have weak arms and leg muscles and breathing issues. Most people with Type-4 SMA are unaware of it until symptoms start. It has no impact on life expectancy.
