SMA is divided into subtypes based on age of onset and maximum function achieved. SMA types 0, 1, 2, 3 and 4 are inherited as autosomal recessive genetic disorders and are associated with mutations in the SMN1 gene, which is located on chromosome 5.
Spinal Muscular Atrophy Type 3
SMA type 3, also known as Kugelberg Welander disease, is a milder type of SMA and is usually diagnosed in children between 18 months old and their early teens, but most are diagnosed before they are 3 years old. People with SMA type 3 learn to walk but fall frequently and have difficulties walking up and down stairs at 2 to 3 years old. Balance can also be a problem, leading to falls.
As with other SMA types, the legs are more severely affected than the arms.
The long-term prognosis for this type of SMA depends on the degree of motor function attained as a child, but in general, muscle weakness progresses much slower, and most people with SMA type 3 walk well into early adulthood.
Weight gain and illness can lead to faster muscle deterioration periods.
People with SMA type 3 usually don’t have many respiratory problems until later in life. The disease can increase the susceptibility to respiratory tract complications, but it doesn’t shorten lifespan.
Approximately 50 percent of the people with SMA type 3 develop scoliosis (curvature of the spine), requiring bracing and/or or surgery. Contractures of the muscles can restrict movement, especially around the hip, knee, and ankle joints.
Physiotherapy and occupational therapy can be useful to determine appropriate aids, adaptive equipment, and home, school, or work modifications to allow people to maintain independence, mobility and energy. It is also important to prevent extra weight gain for better ease of movements.
Speech and language therapists can help with swallowing difficulties that may arise in people with SMA type 3, but this is less common than in people with SMA type 2.
Follow the latest developments for all experimental spinal muscular atrophy treatments on the SMA Therapy Tracker.
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