Type III Spinal Muscular Atrophy (SMA), also known as Kugelberg-Welander disease or intermediate SMA, is a specific form of a rare genetic disorder that affects the motor neurons in the spinal cord.
SMA is classified into four types based on the age of onset and severity of symptoms, with Type III falling in the moderate range. Type III SMA typically manifests in adolescence or adulthood, usually between the ages of 18 months and 60 years old, but the exact timing can vary.
Individuals with Type III SMA generally have the ability to walk independently during their early years, but may experience a gradual loss of motor function over time. Symptoms may include muscle weakness, fatigue, difficulty with running and climbing stairs, as well as frequent falls. However, individuals with Type III SMA often maintain the ability to stand and walk, although they may require mobility aids or devices as the disease progresses.
The underlying cause of Type III SMA is a genetic mutation in the SMN1 gene, which leads to insufficient production of a protein called survival motor neuron (SMN). This protein is crucial for the normal functioning and maintenance of motor neurons. The severity of the subtype is typically influenced by the number of copies of a closely related gene called SMN2, which can partially compensate for the loss of SMN1.
While there is currently no cure for Type III SMA, various supportive treatments and therapies can help manage symptoms, improve quality of life, and slow down disease progression. These may include physical therapy, orthopedic interventions, respiratory support, and assistive devices. Genetic counseling is also recommended for families affected by Type III SMA to understand the inheritance pattern and make informed decisions.
