Spinal muscular atrophy

The severity of SMA and the age of onset can vary depending on the specific genetic mutation. SMA is divided into four types based on the age of onset and the severity of symptoms:

• SMA Type 1 (Werdnig-Hoffmann disease): This is the most severe form of SMA, typically appearing in infancy. Infants with SMA Type 1 have significant muscle weakness, poor muscle tone (hypotonia), and difficulty with swallowing and breathing. They may have difficulty sitting or achieving motor milestones.
• SMA Type 2: This form of SMA usually becomes apparent in early childhood. Children with SMA Type 2 can generally sit unsupported but may have difficulty standing or walking independently. They may experience progressive muscle weakness and respiratory problems.
• SMA Type 3 (Kugelberg-Welander disease): This form of SMA typically starts in childhood or adolescence. Individuals with SMA Type 3 can often walk independently, but they may develop muscle weakness and experience difficulty with climbing stairs or walking long distances.
• SMA Type 4: This is the mildest form of SMA, with symptoms typically appearing in adulthood. People with SMA Type 4 may experience mild muscle weakness and have a normal lifespan.